Covalent Bonding Geometry
材料科学基础教案第一章
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静电力(electrost高分子链
Atomic Structure and Interatomic Bonding
第一章原子结构和键合
第二节 原子间的键合
材料的微观结构（Microstructure of Materials）
决定材料性质最为本质的内在因素： 组成材料各元素原子结构； 原子间相互作用、相互结合； 原子或分子在空间的排列和运动规律； 以及原子集合体的形貌特征。
取代基围绕特定原子在空间的排布规律。
构型
构造
近程结构
单体通过聚合反应连接而成的链状分子，称为高分子链。 高分子中的重复结构单元的数目称为聚合度。 高分子链的化学组成不同，化学和物理性能也不同。
链结构单元的化学组成（the Chemistry of mer unito) 碳链高分子 聚乙烯（见书9）
一、金属键（Metallic bonding）
典型金属原子结构：最外层电子数很少，即价电子（valence electron）极易挣脱原子核之束缚而成为自由电子（Free electron），并在整个晶体内运动，弥漫于金属正离子组成的晶格之中而形成电子云（electron cloud）。 金属中自由电子与金属正离子之间相互作用构成的键合称为金属键。 绝大多数金属均以金属键方式结合，基本特点——电子的共有化
诱导力(induction)
色散力(dispersive force)
贰
壹
材料科学基础名词解释中英
《材料科学基础》名词解释AOrowan mechanism （奥罗万机制）位错绕过第二相粒子，形成包围第二相粒子的位错环的机制。
Austenite(奥氏体)碳在γ-Fe中形成的间隙固溶体称为奥氏体。
B布拉菲点阵除考虑晶胞外形外，还考虑阵点位置所构成的点阵。
Half-coherent interface（半共格相界）两相邻晶体在相界面处的晶面间距相差较大，则在相界面上不可能做到完全一一对应，于是在界面上将产生一些位错，以降低界面弹性应变能。
这时两相原子部分保持匹配，这样的界面称为半共格界面。
Sheet texture（板织构）轧板时形成的组织的择优取向。
Peritectic reaction（包晶反应）固相和液相生成另一成分的固溶体的反应Peritectic segregation（包晶偏析）新生成的固相的芯部保留残余的原有固相，新相本身成分也不均匀。
Peritectic phase diagram（包晶相图）具有包晶反应的相图Peritectoid reaction（包析反应）由两个固相反应得到一个固相的过程为包析反应。
Cellular structure（胞状结构）成分过冷区很小时，固相突出部分局限在很小区域内，不生成侧向枝晶。
Intrinstic diffusion coefficient（本征扩散系数）依赖热缺陷进行的扩散的扩散系数。
Transformed ledeburite（变态莱氏体）渗碳体和奥氏体组成的莱氏体冷却至727℃时奥氏体发生共析反应转变为珠光体，此时称变态莱氏体。
Deformation twins（变形孪晶）晶体通过孪生方式发生塑性变形时产生的孪晶（BCC，HCP）Chill zone（表层细晶区）和低温铸模模壁接触，强烈过冷形成的细小的方向杂乱的等轴晶粒细晶区。
Burger’s vector（柏氏矢量）表征位错引起的晶格点阵畸变大小和方向的物理量。
Asymmetric tilt boundary（不对称倾斜晶界）晶界两侧晶粒不对称的小角度晶界，界面含两套垂直的刃型位错。
化学键分类简述
化学键化学键的种类可分为离子键、共价键及金属键三种，分别做以下介绍：1、离子键与共价键的关系首先，两者没有本质区别，当成键原子的电负性相差越小时，键更倾向共价键，反之键更倾向离子键。
化学研究者通过大量实验数据比对得出电负性相差大于1.7的为离子键，小于1.7的为共价键。
比如AlCl3、FeCl3、CuCl2、Fe(OH)3、MnO2、HgCl2、AgI等都是共价化合物。
数据化的判据是为了将离子化合物与共价化合物的区分相统一，但也有特殊情况，比如HF的电负性相差大于1.7，其实它是共价化合物。
由此看来，键的共价性质与离子性质是统一存在的，只是强弱有别。
但是，离子化合物中可能存在共价键，共价化合物中肯定不存在离子键。
2、离子键 (Ionic Bonding)带相反电荷的阳离子与阴离子以库仑吸引力产生键结，称为离子键。
两个电负度相差极大的原子，一般是金属元素与非金属元素，例如氯和钠，电负度大的氯会从电负度小的钠抢走一个电子，形成稳定Cl-和Na+，两者再以库仑静电力结合在一起。
离子键的强度和形成键结的离子电荷强度成正比与离子距离成反比，离子半径越小或所带电荷越多，负、正离子间的作用就越强；例如钠离子Na+半径比钾离子K+小，则氯化钠NaCl中的离子键较氯化钾KCl中的离子键强。
3、共价键 (Covalent Bonding)两个电负度相近的原子间结合时，通常藉由共享价电子 (valence electron)的方式，使彼此满足八隅体(Octet rule) 电子结构，这种键结为共价键，一般发生在非金属元素与非金属元素之间。
例如:氧分子为两个氧原子各自提供两个价电子共享方式形成共价键。
共价键又可分为极性 (Polar) 共价键与非极性(Non-polar)共价键。
那氯化铝为何是共价化合物？铝的氯化物、溴化物及碘化物在蒸气状态均以Al2X6形式存在，这种二聚体的链状存在形式不同于一般离子化合物（离子化合物一般是立体配位数6、8、12，靠着离子间的相互吸引作用成键），氯化铝的配位数是4，Al以sp3的混成轨域键结(即共价键)，这种键结有相当程度的共价性，属于有离子性的共价化合物，其分子不像离子固体无限延伸。
材料科学基础英文词汇(最新整理)
材料科学基础专业词汇:第一章晶体结构原子质量单位Atomic mass unit (amu) 原子数Atomic number原子量Atomic weight 波尔原子模型Bohr atomic model键能Bonding energy 库仑力Coulombic force共价键Covalent bond 分子的构型molecular configuration 电子构型electronic configuration 负电的Electronegative正电的Electropositive 基态Ground state氢键Hydrogen bond 离子键Ionic bond同位素Isotope 金属键Metallic bond摩尔Mole泡利不相容原理 Pauli exclusion principle 元素周期表Periodic table原子atom 分子molecule分子量molecule weight 极性分子Polar molecule量子数quantum number 价电子valence electron范德华键van der waals bond 电子轨道electron orbitals点群point group 对称要素symmetry elements各向异性anisotropy 原子堆积因数Atomic packing factor(APF)体心立方结构body-centered cubic (BCC) 面心立方结构face-centered cubic (FCC) 布拉格定律bragg’s law 配位数coordination number晶体结构crystal structure 晶系crystal system晶体的crystalline 衍射diffraction中子衍射neutron diffraction 电子衍射electron diffraction晶界grain boundary 六方密堆积hexagonal close-packed(HCP)鲍林规则Pauling’s rules NaCl型结构NaCl－type structure CsCl型结构Caesium Chloride structure 闪锌矿型结构Blende-type structure纤锌矿型结构Wurtzite structure 金红石型结构Rutile structure萤石型结构Fluorite structure 钙钛矿型结构Perovskite-type structure 尖晶石型结构Spinel-type structure 硅酸盐结构Structure of silicates岛状结构Island structure 链状结构Chain structure层状结构Layer structure 架状结构Framework structure滑石talc 叶蜡石pyrophyllite高岭石kaolinite 石英quartz长石feldspar 美橄榄石forsterite各向同性的isotropic 各向异性的anisotropy晶格lattice 晶格参数lattice parameters密勒指数miller indices 非结晶的noncrystalline多晶的polycrystalline 多晶形polymorphism单晶single crystal 晶胞unit cell电位electron states (化合)价valence电子electrons 共价键covalent bonding金属键metallic bonding 离子键Ionic bonding极性分子polar molecules 原子面密度atomic planar density衍射角diffraction angle 合金alloy粒度,晶粒大小grain size 显微结构microstructure显微照相photomicrograph 扫描电子显微镜scanning electronmicroscope (SEM)重量百分数weight percent 透射电子显微镜 transmission electronmicroscope (TEM)四方的tetragonal 单斜的monoclinic配位数coordination number材料科学基础专业词汇:第二章晶体结构缺陷缺陷defect, imperfection 点缺陷point defect线缺陷line defect, dislocation 面缺陷interface defect体缺陷volume defect 位错排列dislocation arrangement位错线dislocation line 刃位错edge dislocation螺位错screw dislocation 混合位错mixed dislocation晶界grain boundaries 大角度晶界high-angle grainboundaries 小角度晶界tilt boundary, 孪晶界twin boundaries位错阵列dislocation array 位错气团dislocation atmosphere位错轴dislocation axis 位错胞dislocation cell位错爬移dislocation climb 位错聚结dislocation coalescence位错滑移dislocation slip 位错核心能量dislocation core energy位错裂纹dislocation crack 位错阻尼dislocation damping位错密度dislocation density 原子错位substitution of a wrongatom间隙原子interstitial atom 晶格空位vacant lattice sites间隙位置interstitial sites 杂质impurities弗伦克尔缺陷Frenkel disorder 肖脱基缺陷Schottky disorder主晶相the host lattice 错位原子misplaced atoms缔合中心Associated Centers. 自由电子Free Electrons电子空穴Electron Holes 伯格斯矢量Burgers克罗各-明克符号K roger Vink notation 中性原子neutral atom材料科学基础专业词汇:第二章晶体结构缺陷-固溶体固溶体solid solution 固溶度solid solubility化合物compound 间隙固溶体interstitial solid solution置换固溶体substitutional solid solution 金属间化合物intermetallics不混溶固溶体immiscible solid solution 转熔型固溶体peritectic solid solution有序固溶体ordered solid solution 无序固溶体disordered solid solution 固溶强化solid solution strengthening 取代型固溶体Substitutional solidsolutions过饱和固溶体supersaturated solid solution 非化学计量化合物Nonstoichiometric compound材料科学基础专业词汇:第三章熔体结构熔体结构structure of melt 过冷液体supercooling melt玻璃态vitreous state 软化温度softening temperature粘度viscosity 表面张力Surface tension介稳态过渡相metastable phase 组织constitution淬火quenching 退火的softened玻璃分相phase separation in glasses 体积收缩volume shrinkage材料科学基础专业词汇:第四章固体的表面与界面表面surface 界面interface同相界面homophase boundary 异相界面heterophase boundary晶界grain boundary 表面能surface energy小角度晶界low angle grain boundary 大角度晶界high angle grain boundary 共格孪晶界coherent twin boundary 晶界迁移grain boundary migration 错配度mismatch 驰豫relaxation重构reconstuction 表面吸附surface adsorption表面能surface energy 倾转晶界titlt grain boundary扭转晶界twist grain boundary 倒易密度reciprocal density共格界面coherent boundary 半共格界面semi-coherent boundary 非共格界面noncoherent boundary 界面能interfacial free energy应变能strain energy 晶体学取向关系crystallographicorientation惯习面habit plane材料科学基础专业词汇:第五章相图相图phase diagrams 相phase组分component 组元compoonent相律Phase rule 投影图Projection drawing浓度三角形Concentration triangle 冷却曲线Cooling curve成分composition 自由度freedom相平衡phase equilibrium 化学势chemical potential热力学thermodynamics 相律phase rule吉布斯相律Gibbs phase rule 自由能free energy吉布斯自由能Gibbs free energy 吉布斯混合能Gibbs energy of mixing 吉布斯熵Gibbs entropy 吉布斯函数Gibbs function热力学函数thermodynamics function 热分析thermal analysis过冷supercooling 过冷度degree of supercooling杠杆定律lever rule 相界phase boundary相界线phase boundary line 相界交联phase boundarycrosslinking共轭线conjugate lines 相界有限交联phase boundarycrosslinking相界反应phase boundary reaction 相变phase change相组成phase composition 共格相phase-coherent金相相组织phase constentuent 相衬phase contrast相衬显微镜phase contrast microscope 相衬显微术phase contrastmicroscopy相分布phase distribution 相平衡常数phase equilibriumconstant相平衡图phase equilibrium diagram 相变滞后phase transition lag相分离phase segregation 相序phase order相稳定性phase stability 相态phase state相稳定区phase stabile range 相变温度phase transitiontemperature相变压力phase transition pressure 同质多晶转变polymorphictransformation同素异晶转变allotropic transformation 相平衡条件phase equilibriumconditions显微结构microstructures 低共熔体eutectoid不混溶性immiscibility材料科学基础专业词汇:第六章扩散活化能activation energy扩散通量diffusion flux浓度梯度concentration gradient菲克第一定律Fick’s first law菲克第二定律Fick’s second law相关因子correlation factor稳态扩散steady state diffusion非稳态扩散nonsteady-state diffusion 扩散系数diffusion coefficient跳动几率jump frequency填隙机制interstitalcy mechanism晶界扩散grain boundary diffusion 短路扩散short-circuit diffusion上坡扩散uphill diffusion下坡扩散Downhill diffusion互扩散系数Mutual diffusion渗碳剂carburizing浓度梯度concentration gradient 浓度分布曲线concentration profile扩散流量diffusion flux驱动力driving force间隙扩散interstitial diffusion自扩散self-diffusion表面扩散surface diffusion空位扩散vacancy diffusion扩散偶diffusion couple扩散方程diffusion equation扩散机理diffusion mechanism扩散特性diffusion property无规行走Random walk达肯方程Dark equation柯肯达尔效应Kirkendall equation本征热缺陷Intrinsic thermal defect本征扩散系数Intrinsic diffusion coefficient离子电导率Ion-conductivity空位机制Vacancy concentration材料科学基础专业词汇:第七章相变过冷supercooling 过冷度degree of supercooling 晶核nucleus 形核nucleation形核功nucleation energy 晶体长大crystal growth均匀形核homogeneous nucleation 非均匀形核heterogeneous nucleation形核率nucleation rate 长大速率growth rate 热力学函数thermodynamics function临界晶核critical nucleus 临界晶核半径critical nucleus radius枝晶偏析dendritic segregation 局部平衡localized equilibrium平衡分配系数equilibriumdistributioncoefficient有效分配系数effective distribution coefficient成分过冷constitutional supercooling 引领（领先）相leading phase共晶组织eutectic structure 层状共晶体lamellar eutectic伪共晶pseudoeutectic 离异共晶divorsed eutectic表面等轴晶区chill zone 柱状晶区columnar zone中心等轴晶区equiaxed crystal zone 定向凝固unidirectional solidification 急冷技术splatcooling 区域提纯zone refining单晶提拉法Czochralski method 晶界形核boundary nucleation位错形核dislocation nucleation 晶核长大nuclei growth斯宾那多分解spinodal decomposition有序无序转变disordered-order transition马氏体相变martensite phase transformation 马氏体martensite材料科学基础专业词汇:第八、九章固相反应和烧结固相反应solid state reaction 烧结sintering烧成fire 合金alloy再结晶Recrystallization 二次再结晶Secondary recrystallization 成核nucleation 结晶crystallization子晶，雏晶matted crystal 耔晶取向seed orientation异质核化heterogeneous nucleation 均匀化热处理homogenization heattreatment铁碳合金iron-carbon alloy 渗碳体cementite铁素体ferrite 奥氏体austenite共晶反应eutectic reaction 固溶处理solution heat treatment。
动态共价键 超材料 -回复
动态共价键超材料-回复什么是动态共价键（Dynamic Covalent Bonding）？如何构建超材料（Metamaterials）并应用于我们的生活中？这是一个引人注目的领域，涉及颇为复杂的化学和材料学原理。
在本文中，我将一步一步回答这些问题，并探讨这两个领域的关系以及未来的发展方向。
首先，让我们从动态共价键开始。
动态共价键是一种特殊的化学键形式，其特点是能够通过外部刺激改变键的强度或断裂。
与常见的共价键不同，动态共价键可以在不损失原子间连接的情况下进行动态调整。
这使得动态共价键具有许多独特的性质和潜在的应用。
动态共价键的发现与发展主要建立在有机化学的基础上。
通过利用有机化学中的一些基本反应，如亲核加成、羟醇反应或巯基反应，可以构建具有动态共价键的分子。
这些反应通常是可逆的，并且可以通过适当的条件进行断裂和重新组合。
这使得动态共价键非常有吸引力，因为可以通过调整外部条件来实现分子的重组和结构的变化。
在构建超材料方面，动态共价键发挥了重要作用。
超材料是一种人工合成的材料，具有非常特殊的性质和功能。
通过将不同类型的物质结合在一起，并精确地设计其结构和组织方式，超材料可以呈现出一些传统材料所不具备的特点，如负折射、负折射率、超常弯曲等。
这些特点赋予了超材料在光学、声学、电磁等领域的广泛应用。
动态共价键的特性使得其能够在超材料的构建中发挥重要作用。
通过利用动态共价键的可逆性和调控性，可以精确地控制超材料的结构和性质。
例如，通过调整外部条件，如温度、溶剂、光照等，可以实现超材料的重组或转变。
这为超材料的设计和制备提供了更大的灵活性和多样性。
然而，要实现动态共价键超材料的实际应用仍然面临着一些挑战。
首先，动态共价键材料的稳定性是一个关键问题。
要实现可控的重组和转变，需要确保动态共价键在所需条件下能够保持足够的稳定性。
此外，动态共价键的可逆性和调控性也需要进一步研究和理解。
如何精确地控制外部条件以实现所需的结构和性质变化仍然是一个需要解决的问题。
alevel bonding指化学键和分子间作用力
alevel bonding指化学键和分子间作用力A-level bonding refers to the various types of chemical bonds and intermolecular forces that are studied at the A-level (advanced level) of chemistry education. These include:1. Ionic bonding: This occurs when there is a transfer of electrons between atoms, resulting in the formation of positive and negative ions. The attraction between these ions is what holds the bond together. Ionic bonds are typically found in compounds that involve metals andnon-metals.2. Covalent bonding: In covalent bonding, atoms share electrons to forma bond. This can occur between atoms of the same element or different elements. Covalent bonds are typically found in molecules and can be classified as either polar or non-polar, depending on the electronegativity difference between the atoms involved.3. Metallic bonding: This type of bonding is found in metals. It involves the delocalization of valence electrons, which creates a "sea" of electrons that hold the metal ions together. Metallic bonding is responsible for the characteristic properties of metals, such as their high electrical and thermal conductivity and malleability.In addition to these types of chemical bonding, A-level chemistry also covers intermolecular forces, which are the forces of attraction between molecules. These forces include:1. London dispersion forces: These are the weakest intermolecular forces and are caused by temporary fluctuations in electron distribution within molecules. London dispersion forces are present in all molecules, but they become stronger with increasing molecular size and shape.2. Dipole-dipole interactions: These occur between polar molecules and are caused by the attraction between the positive end of one molecule and the negative end of another molecule. Dipole-dipole interactions are stronger than London dispersion forces.3. Hydrogen bonding: This is a special type of dipole-dipole interaction that occurs when a hydrogen atom is bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine) and is attracted to another electronegative atom. Hydrogen bonding is responsible for many of the unique properties of substances like water.Overall, A-level bonding encompasses the study of chemical bondswithin molecules and the intermolecular forces that operate between molecules. Understanding these bonding forces is crucial for understanding the properties and behavior of substances in chemistry.。
共价结合法英文
共价结合法英文Covalent Bonding。
Covalent bonding is a fundamental concept in chemistry that describes the sharing of electron pairs between atoms. It is one of the main types of chemical bonding, along with ionic bonding and metallic bonding. In covalent bonding, atoms share electrons in order to achieve a stable electron configuration and form molecules.When two atoms come close together, their electron clouds overlap, allowing the electrons to be shared between the atoms. This sharing of electrons creates a bond between the atoms and holds them together in a molecule. The shared electrons are attracted to both nuclei, creating a strong bond.Covalent bonds can be classified as either nonpolar or polar, depending on the electronegativity difference between the atoms involved. In a nonpolar covalent bond, the electrons are shared equally between the atoms because they have the same or similar electronegativities. Examples of nonpolar covalent compounds include oxygen gas (O2) and nitrogen gas (N2).On the other hand, in a polar covalent bond, the electrons are not shared equally because the atoms have different electronegativities. The atom with the higher electronegativity attracts the shared electrons more strongly, creating a partial negative charge. The atom with the lower electronegativity has a partial positive charge. Examples of polar covalent compounds include water (H2O) and ammonia (NH3).Covalent bonds can also be classified as single, double, or triple bonds, depending on the number of electron pairs shared between the atoms. In a single bond, one pair of electrons is shared, while in a double bond, two pairs of electrons are shared. In a triple bond, three pairs of electrons are shared. The strength of the bond increases with the number of shared electron pairs.The properties of covalent compounds are determined by the nature of the covalent bonds within them. Covalent compounds generally have low melting and boiling pointsbecause the intermolecular forces between the molecules are weak. They are also usually poor conductors of electricity because they do not contain freely moving charged particles.However, there are exceptions to these general properties. For example, some covalent compounds, such as diamond and quartz, have high melting and boiling points due to the strong covalent bonds within their structures. Additionally, certain covalent compounds, such as acids and bases, can conduct electricity when dissolved in water.In conclusion, covalent bonding is a crucial concept in chemistry that involves the sharing of electron pairs between atoms. It allows atoms to achieve a stable electron configuration and form molecules. Covalent bonds can be nonpolar or polar, and they can be single, double, or triple bonds. The properties of covalent compounds depend on the nature of the covalent bonds within them. Understanding covalent bonding is essential for understanding the behavior and properties of many substances in the world around us.。
材料科学基础§1-2 结合键
金刚石结构
共价晶体性能：强度高，硬度高，脆性大，熔点高，沸点高 和挥发性低。
三、金属键（Metallic Bonding） 金属键：金属中自由电子与金属正离子之间构成的键。 实质：金属最外层电子数很少（通常s、p 价电子数少 于4），即价电子（valence electron）极易挣脱原子核
之束缚而成为自由电子（Free electron），形成电子云
（electron cloud）。 特点：电子共有化，既无饱和性又无方向性，容易形 成低能量密堆结构。
金属键材料特点： 良好的导电性和导热性。 正的电阻温度系数。 不透明并呈现特有的金属光泽。
良好的塑性变形能力，好的强韧性。
四. 范德华键（Van der Waals Bonding) 范德华键：材料中分子间存在的一种弱的作用力。 极性分子：共价电子对偏于某一成键电子 非极性分子：共价电子对位于成价电子中间
性质：熔点和硬度均较高，热膨胀系统小， 但脆性大。 良好电绝缘体。
二、共价键（Covalent Bonding） 亚金属（C、Si、Sn、Ge）、聚合物和无机非金属 材料。
实质：由二个或多个电负性差不大的原子间通过共用电 子对形成。 特点：饱和性、配位数较小、方向性 在形成共价键时，为使电子云达到最大限度的重叠，共 价键就有方向性，键的分布严格服从键的方向性。 当一个电子和另一个电子配对以后就不再和第三个电子 配对了，成键的公用电子对数目是一定的，这就是共价 键的饱和性。
不同的键对应着不同的电子分布方式，但都满足一个共 同的条件，即键合后各原子的外层电子结构要成为稳定的 结构，也就是隋性气体原子的外层 “八电子层”结构 （即ns2 np6 结构）。
离子键
Ionic Bonding
covalent bond结构
covalent bond结构Covalent Bond Structure.The concept of covalent bonding is a fundamental aspect of chemistry, and it plays a crucial role in understanding the structure and behavior of molecules. Covalent bonds are formed when two atoms share one or more pairs of electrons, creating a strong bond that holds the atoms together. This type of bonding is prevalent in many organic compounds and is essential for the formation of complex molecules.The structure of a covalent bond is based on the sharing of electrons between two atoms. Each atom contributes one or more electrons to the bond, and these electrons are shared in such a way that the resulting molecule is held together by the attractive forces between the positively charged nuclei and the negatively charged shared electrons.The strength of a covalent bond is determined by thenumber of shared electrons and the distance between the nuclei of the bonded atoms. The more electrons that are shared, the stronger the bond will be. Additionally, the distance between the nuclei also affects the strength of the bond, with shorter distances resulting in stronger bonds.Covalent bonds can be classified as single, double, or triple bonds, depending on the number of electron pairsthat are shared between the atoms. In a single bond, one pair of electrons is shared, while in a double bond, two pairs are shared, and in a triple bond, three pairs are shared. These different types of bonds result in varying bond strengths and bond lengths, which in turn affect the properties of the molecules.The structure of covalent bonds also contributes to the overall shape of molecules. The arrangement of atoms and the way in which they are bonded together determine the three-dimensional shape of the molecule. This, in turn, affects the molecule's chemical and physical properties, such as its reactivity, polarity, and solubility.In summary, the structure of a covalent bond is based on the sharing of electrons between atoms, resulting in a strong bond that holds the atoms together. The number of shared electrons and the distance between the bonded atoms determine the strength of the bond, and the type of bond (single, double, or triple) affects the overall shape and properties of the molecule. Understanding the structure of covalent bonds is essential for comprehending the behavior of molecules and the interactions between atoms in chemical reactions.。
离子键共价键
离子键共价键
离子键共价键作为一种特定的单元类型，在生物物理学中扮演着重要的角色，同样在互联网的发展以及应用中，也有着不可忽略的重要性。
离子键共价键(Ionic Bonding and Covalent Bonding,简称IBC)是化学中最重要的单元之一，本质上是由离子或分子之间产生的力量而发生的一种气态结构。
这种力量是离子表面与离子表面或分子表面相互作用的结果，在离子或分子之间建立起互补的关系，从而形成稳定的构造。
在现代的互联网发展进程中，离子键共价键也受到了极其重要的应用，许多网络技术，如物联网、移动互联网等，都建立在离子键共价键的原理上，其最显著的特征就是动态性。
凭借着其动态的网络结构，离子键共价键可以有效地连接各种设备及用户，去构建复杂的网络，进而支持网络数据传输及信息交换。
此外，离子键共价键还可以用于保护网络安全，特别是在今天网络的发展及扩张，以及各种安全威胁不断出现的情况下，用离子键共价键机制可以更有效地保护网络安全，并且它具有枢纽本身的强大加密机制功能。
总之，离子键共价键在互联网行业也是一种不可忽视的技术，可以为我们在网络技术、网络连接及网络安全等领域带来巨大的便利，它为网络技术及应用的开发提供了可靠的途径。
covalent
covalentCovalent Bonds: Understanding the Strongest Bonds in ChemistryIntroductionIn the fascinating world of chemistry, there are various types of chemical bonds that hold atoms together in molecules. One of the strongest and most common types of bonds is the covalent bond. In this document, we will delve into the concept of covalent bonds, explore their properties, and discuss their significance in various aspects of everyday life.1. What are Covalent Bonds?Covalent bonds are a type of chemical bond formed between two atoms when they share one or more pairs of electrons. In this type of bonding, atoms strive to achieve a stable electron configuration by completing their outermost electron shells. By sharing electrons with another atom, both atoms can achieve a more stable state, resulting in the formation of a covalent bond.2. Properties of Covalent Bonds2.1. Electron SharingThe defining characteristic of a covalent bond is the sharing of electrons between atoms. Unlike ionic bonds, where electrons are transferred from one atom to another, covalent bonds involve a mutual sharing of electrons. This sharing creates an attractive force that holds the atoms together.2.2. Bond StrengthCovalent bonds are among the strongest types of chemical bonds because the shared electrons are held relatively close to the positively charged nuclei of both atoms. This strong attraction between the electrons and the nuclei contributes to the stability and strength of covalent bonds.2.3. Bond Length and Bond EnergyThe length and energy of a covalent bond are related. The length of a covalent bond depends on the types of atoms involved and their distance from each other. Generally,shorter bond lengths correspond to stronger bonds. Bond energy, on the other hand, refers to the amount of energy required to break the bond. Higher bond energies indicate stronger bonds.3. Types of Covalent BondsCovalent bonds can be further classified into different types based on the way electrons are shared between atoms. The most common types include:3.1. Single Covalent BondIn a single covalent bond, two atoms share one pair of electrons. This is the simplest form of covalent bonding and is commonly found in molecules such as hydrogen (H2) and chlorine (Cl2).3.2. Double Covalent BondA double covalent bond involves the sharing of two pairs of electrons between two atoms. This type of bond is strongerthan a single covalent bond and can be found in molecules such as oxygen (O2) and carbon dioxide (CO2).3.3. Triple Covalent BondThe triple covalent bond is the strongest type of covalent bond, as it involves the sharing of three pairs of electrons between two atoms. Examples of molecules with triple covalent bonds include nitrogen (N2) and acetylene (C2H2).4. Importance of Covalent Bonds4.1. Biological SystemsCovalent bonds are essential in the structure and functioning of biological systems. In organic molecules such as proteins and DNA, covalent bonds hold atoms together and determine the three-dimensional structure, allowing for precise functionality and replication.4.2. Material ScienceCovalent bonds play a crucial role in the development of advanced materials. Substances like polymers, ceramics, and semiconductors rely on strong covalent bonds for their stability and unique properties, such as high strength, heat resistance, and electrical conductivity.4.3. PharmaceuticalsUnderstanding covalent bonds is vital in the design and development of pharmaceutical drugs. Covalent bonds between drugs and targets can lead to long-lasting effects, improving drug efficacy and reducing the required dosages.5. ConclusionCovalent bonds are a fundamental concept in chemistry, encompassing a wide range of applications and importance. From biological systems to advanced materials and pharmaceuticals, the understanding and manipulation of covalent bonds have revolutionized various scientific fields. By exploring the properties and types of covalent bonds, we gain a deeper appreciation for their significance and the roles they play in our everyday lives.。
USP关于色谱柱填料的规定
我们在实验中常常用到USP作为检验依据，其中有一些关于色谱柱的要求现将其中个色谱柱要求罗列如有不恰当的请大家指正L1和L8是美国药典(USP)规定的色谱柱编号，其实就是C18柱和NH2柱。
下面是对应的色谱柱类型。
L1：十八烷基键合多孔硅胶或无机氧化物微粒固定相，简称C18或ODSL2：30～50um表面多孔薄壳型键合C18(ODS)固定相L3：多孔硅胶微粒即一般的硅胶柱L4：30～50um表面多孔薄壳型硅胶L5：30～50um表面多孔薄壳型氧化铝L6：30～50um实心微球表面包覆磺化碳氟聚合物－强阳离子交换固定相L7：全多孔硅胶微粒键合C8官能团固定相简称C8柱L8：全多孔硅胶微粒键合非交联NH2固定相简称NH2柱L9：强酸性阳离子交换基团键合全多孔不规则形硅胶固定相L10：多孔硅胶微球键合氰基固定相（CN）简称CN柱L11：键合苯基多孔硅胶微球固定相简称苯基柱L12：无孔微球键合季胺功能团的强阴离子填料L13：三乙基硅烷化学键合全多孔硅胶微球固定相（C1）简称C1柱L14:10um硅胶化学键合强碱性季铵盐阴离子交换固定相简称SAX柱L15：已基硅烷化学键合全多孔硅胶微球固定相简称C6柱L16：二甲基硅烷化学键合全多孔硅胶微粒固定相L17：氢型磺化交联苯乙烯-二乙烯基苯共聚物,强阳离子交换树脂L18: 3～10um全多孔硅胶化学键合胺基（NH2）和氰基（CN）L19：钙型磺化交联苯乙烯－二乙烯基苯共聚物，强阳离子交换树脂L20：二羟基丙烷基化学键合多孔硅胶微球固定相（Diol）简称二醇基柱L21：刚性苯乙烯－二乙烯基苯共聚物微球L22：带有磺酸基团的多孔苯乙烯阳离子交换树脂L23：带有季胺基团的聚甲基丙烯酸甲酯或聚丙烯酸酯多孔离子交换树脂L24：表面含有大量羟基的半刚性聚乙烯醇亲水凝胶L25：聚甲基丙烯酸酯树脂交联羟基醚（表面含有残余羧基功能团）树脂。
能分离分子量100～5000MW范围的水溶性中性、阳离子型及阴离子型聚合物（用聚氧乙烯测定）的固定相L26：丁基硅烷化学键合全多孔硅胶微球固定相L27：30～50um的全多孔硅胶微粒L28：多功能载体，100?的高纯硅胶加以氨基键合以及C8反相键合的官能团L29: 氧化铝,反相键合,含碳量低,氧化铝基聚丁二稀小球,5um，孔径80?L30: 全多孔硅胶键合乙基硅烷固定相L31: 季胺基改性孔径2000?的交联苯乙烯和二乙烯基苯(55%)强阴离子交换树脂L32: L-脯氨酸铜配合物共价键合于不规则形硅胶微粒的配位体的交换手性色谱填料L33: 能够分离分子量4000～40000MW范围蛋白质分子的球形硅胶固定相,pH稳定性好L34：铅型磺化交联苯乙烯－二乙烯基苯共聚物强阳离子交换树脂，9um球形L35：锆稳定的硅胶微球键合二醇基亲水分子单层固定相，孔径150?L36: 5um胺丙基硅胶键合L-苯基氨基乙酸－3,5二硝基苯甲酰L37：适合分离分子量2000～40,000Mw的聚甲基丙烯酸酯凝胶L38：水溶性甲基丙烯酸酯基质SEC色谱柱L39：亲水全多孔聚羟基甲基丙烯酸酯色谱柱L40：Tris 3,5－二甲基苯基氨基甲酸酯纤维素涂覆多孔硅胶微球L41：球形硅胶表面固定α1酸糖蛋白固定相L42: C8和C18硅烷化学键合多孔硅胶固定相L43: 硅胶微球键合五氟代苯基固定相L44: 多功能固定相,60 ?高纯硅胶基质键合磺酸阳离子交换功能团和C8反相功能团L45: β-环糊精键合多孔硅胶微球L46: 季胺基改性苯乙烯-二乙烯基苯聚合物微球液相色谱柱USP column PackingL1 —— Octadecyl silane chemically bonded to porous silica or ceramic micro-particles,3 to 10um in diameterL2 —— Octadecyl silane chemically bonded to silica gel of a controlled surface porosity that has been bonded to a solid spherical core, 30 to 50um in diameter.L3 —— Porous silica particles, 5 to 10um in diameter.L4 —— Silica gel of controlled surface porosity bonded to a solid spherical core, 30 to 50um in diameter.L5 —— Alumina of controlled surface porosity bonded to a solid spherical core , 30 to 50um in diameter.L6 —— Strong cation –exchange packing-sulfonated fluorocarbon polymer coated on a solid spherical, 30 to 50um in diameter.L7 —— Octylsilane chemically bonded to totally porous silica particles , 3 to 10um in diameter.L8 —— An essentially monomolecular layer of aminopropylsilane chemically bonded to totally porous silica gel support, 10um in diameter.L9 —— 10um irregular or spherical layer of aminopropylsilane chemically bonded, strongly acidic cation-exchange coating.L10- Nitrile groups chemically bonded to porous silica particles, 3 to 10um in diameter.L11- Phenyl group chemically bonded to porous silica particles, 5 to 10um in diameter.L12- A strong anion-exchange packing made by chemically bonding a quaternary ammonium anion-exchange coating.L13- Trimethylsilane chemically bonded to porous silica particles, 3 to 10um in diameter.L14 – Silica gel 10um in diameter having a chemically bonding a quaternary ammonium anion-exchange coating.L15 – Hexylsilane chemically bonded to totally porous silica particles, 3 to 10um in diameter.L16 – Dimethylsilane chemically bonded to porous silica particles, 5 to 10um in diameter.L17_ Strong cation-exchange resin consisting of sulfonatedcross-linked styrene-divinylbenzene copolymer in the hydrogen from, 7 to 11um in diameter.L18 – Amion and cyano groups chemically bonded to porous silica particles, 3 to 10um in diameter.L19 – Strong cation-exchange resin consisting of sulfonatedcross-linked styrene-divilbenzene copolymer in the calcaium from, about 10um in diameter.L20- Dihydroxypropane groups chemically bonded porous silica particles , 5 to 10um in diameter.L21 – A rigid, spherical styrene-divinylbenxene copolymer, 5 to10um in diameter.L22 – A cation-exchange resin made of porous polystyrene gel with sulfonic acid group, about 10um in diameter.L23 – An cation-exchange resin made of porous polymethacrylate or polyacrylate gel with quaternary ammonium groups, about 10um in size.L24 — A semi-right hydrophilic gel consisting of vinyl polymers with numerous hydroxyl groups on the matrix surface , 32 to 63um in diameter.5L25 _Packing having the capacity to separate compounds with a molecular weight range from 100-5000 (as determined by polyethylene oxide), applied to neutral, and cationic water-soluble polymers. A polymethacrylate resin base, cross-linked withpoly-hydroxylated ether (surface contained some residual carboxylfunctional groups) was fund suitable.L26- Butyl silica chemically bonded to totally porous silica particles, 5 to 10um in diameter.L27 _ Porous silica particles, 30 to 5um in diameter.L28 – A multifunctional support, which consists of a high purity, 100 Å, spherical silica substrate that has been bonded with anionic exchange, amine functionality in addition to a conventional reversed phase C8 functionality.L29_ Gamma alumina, reverse-phase, low carbon percentage by weight, alumina-based polybutadiene, spherical particles. 5um in diameter with a pore volume of 80 ÅL30- Ethyl silica chemically bonded to totally porous silica particles, 3 to 10um in diameter.L31 – A strong anion-exchange resin-quaternary amine bonded on latex particles attached to a core of 8.5um macroporous particles having a pore size of 2000Å and consisting of ethylvinylbenzene cross-linked with 55% divinylbenzene.L32 – A chiral ligand-exchange packing-L-proline copper complex covalently bonded to irregularly shaped silica particles, 5 to 10um in diameter.L33- Packing having the capacity to separate dextrans by molecular size over a range of 4000 to 500000 Da. It is spherical, silica-based, and processed to provide PH stability.6L34 – Strong cation-exchange resin consisting of sulfonatedcross-linked styrene-divinybenzene copolymer in the lead form, about 9um in diameter.L35- A zirconium-stabilized spherical silica packing with a hydrophilic(diol-type) molecular monolayer bonded phase having p pore size of 150Å.L36 – A 3,5-dinitrobenzoyl derivative of L-phenylglycine covalently bonded to 5um aminopropyl silica.L37 – Packing having the capacity to separate proteins by molecular size over range of 2000 to 40000Da. It is a polymethacrylate gel.L38 – A methacrylate-based size-exclusion packing forwater-soluble samples.L39- A hydrophilic polyhydroxymethacrylate gel of totally porous spherical resin.L40 – Cellulose tris-3,5-dimethylphenylcarbmate coated porous silica particles, 5 to 20umin diameter.L40—Cellulose tris-3,5-dimethylphenylcarbamate coated porous silica particles,5 to 20 μm indiameter.L41－Immobilized а1 acid glycoprotein on spherical silica particles,5μm in diameter.L42—Octylsilane and octadecylsilane groups chemically bonded to porous silica particles, 5μm in diameter.L43—Pentafluorophenyl groups chemically bonded to silica particles by a propyl spacer, 5 to 10μm in diameter.L44—A multifunctional support,which consists of a highpurity,60Å,spherical silica substrate that has been bonded with a cationic exchanger,sulfonic acid functionalityin addition to conventional reversed phase C8 functionality.L45—Beta cyclodextrin bonded to porous silica particles, 5 to 10μm in diameter.L46—Polystyrene/divinylbenzene substrate agglomerated with quaternary amine func tionalized latex beads, 10μm in diameter.L47—High-capacity anion-exchange microporous substrate,funlly functionalized with trimethlyamine groups,8μm in diameter.7L48－Sulfonated,cross-linked polystyrene with an outer layer of submicron,porous,anion-excha nge microbends 15μm in diameter.L49－A reversed-phase packing made by coating a thin layer of polybutadiene onto spherical porous zirconia particles,3 to 10μm in diameter.8L50－Multifunction resin with reversed-phase retention and strong anion-exchange functionalities.The resin consists of ethylvinylbenzene 55％cross-linked with divinylbenzene copolymer,3 to 15μm in diameter,and a surface area not less than 350㎡per g.Substrate is coated with quaternary ammonium functionalized latex particles consisting of styrene cross-linked with divinylbenzene.9L51—Amylosetris-3,5-dimethylphenylcarbamate-coated,porous,spherical,silica particles, 5 to 10μm in diameter.10L52—A strong cation exchange resin made of porous silica with sulfopropyl groups,5 to 10μm in diameter.11L53—Weak cation-exchange consisting of ethylvinylbenzene,55％cross-linked with divinylbenzene copolymer, 3 to 15μm in diameter.Substrate is surface grafted with carboxylic acidand/orphosphoric acid functionalized monomers.Capacity not less than 500μEq/column.12L54－A size exclusion medium made of covalent bonding of dextran to highly cross-linked porous agarose beads,about 13 μm in diameter.13L55－A strong cation-exchange resin made of porous silica coated with polybutadiene-maleic acid copolmer,about 5 μm in diameter.14L56－Isopropyl silane chemically bonded to totally porous silica paryicles,3 to 10μm in diameter.15L57－A chiral recognition protein,ovomucoid,chemically onded to silica particles,about 5μm in diameter,with a pore size of 120ÅL58－Strong cation-exchange resin consisting of sulfonatedcross-linked styrene-divinylbenzene copolymer in the sodium form,about7to 11μm in diameter,16▲ L59－Packing having the capoacity to separate proteins bymolecular weight over the range of 10 to 500kDa.It issph erical(10μm),silica-based, and processed to provide hydrophilic characteristics and pH stability.17▲USP28▲ L60－Spherical,porous silica gel,3 or 5μm in diameter,the surface of which has been covalently modified withpalmitamido-propyl groups and endcapped with acetamidopropyl groups to a ligand density of about 6 μmoles per ㎡.18▲USP28L61 A hydroxide selective strong anion-exchange resin consisting of a highly cross-linked core of 13 µm microporous particles having a pore size less than 10 Angstrom units and consisting of ethylvinylbenzene cross-linked with 55% divinylbenzene with a latex coating composed of 85 nm diameter microbeads bonded with alkanol quartenary ammonium ions (6%) L62 C30 silane bonded phase on a fully porous spherical silica, 3 to 15 µm in diameterL63 Glycopeptide teicoplanin linked through multiple covalent bonds to a 100 Angstrom units spherical silica.L64 Strongly basic anion exchange resin consisting of 8% crosslinked styrene divinylbenzene copolymer with a quartenary ammonium group in the chloride form, 45 to 180 µm in diameter.L65 Strongly acidic cation exchange resin consisting of 8% sulfonated crosslinked styrene divinylbenzene copolymer with a sulfonic acid group in the hydrogen form, 63 to 250 µm in diameter. L66 A crown ether coated on a 5 µm particle size silica gel substrate. The active site is (S)-18-crown-6-ether.L67 Porous vinyl alcohol copolymer with a C18 alkyl group attached to the hydroxyl group of the polymer.L68 Spherical, porous silica, 10 µm or less in diameter, the surface of which has been covalently modified with alkyl amide groups and not endcapped.L69 Ethylvinylbenzene/divinylbenzene substrate agglomerated with quartenary amine functionalized 130 nm latex beads, about 6.5 µm in diameter.L70 Cellulose tris(phenyl carbamate) coated on 5 µm silicaL71 A rigid, spherical, polymethacrylate, 4 to 6 µm in diameter L72 (S)-phenylglycine and 3,5-dinitroanaline urea linkage covalently bonded to silica.L73 A rigid spherical polydivinylbenzene particle, 5 to 10 µm in diameterL74 A strong anion-exchange resin consisting of a highly cross-linked core of 7 µm macroporous particles having a 100 Angstroms average pore size and consisting of ethylvinylbenzene cross-linked with 55% divinylbenzene and an anion-exchange layer grafted to the surface, which is functionalized with alkyl quartenary ammonium ions.气相色谱柱PhasesG1－Dimethylpolysilxane oil.G2－Dimethylpolysilxane gum.G3－50%Phenyl-50% methylpolysiloxane.G4－Diethylene glycol succinate polyester.G5－3-Cyanopropylpolysiloxane.G6－Trifluoropropylmethylpolysiloxane.G7－50%3-Cyanopropyl-50%phenylmethylsilicone.G8－80% Bis(3-cyanopropyl)-20%3-cyanopropylphenylpolysi-loxane(percentages refer to molar substitution).G9－Methylvinylpolysiloxane.G10－Polyamide formed by reacting a C36 dicarboxylic acid with 1,3-di-4-piperidylpropane and piperidine in the respective mole ratios of 1.00:0.90:0.20.G11－Bis(2-ethylhexyl)sebacate polyester.G12－Phenyldiethanoamine succinate polyester.G13－Sorbitol.G14－Polyethylene glycol(av.mol.wt.of 950 to 1050).G15－Polyethylene glycol(av.mol.wt.of 3000 to 3700).G16－Polyethylene glycol compound(av.mol.wt.about 15,000).A high molecular weight compound of polyethene glycol with a diepoxide linker.Available commercially as Polyethylene Glycol Compound 20M,or as Carbowax 20M,from suppliers of chromatographic reagents.G17－75% Phenyl-25% methylpolysiloxane.G18－Polyalkylene glycol.G19－25% Phenyl-25% cyanopropyl-50% methylsilicone.G20－Polyethylene glycol(av.mol.wt.of 380 to 420).G21－Neopentyl glycol succinate.G22－Bis(2-ethylhexyl)phthalate.G23－Polyethyl glycol adipate.G24－Diisodecyl phthalate.G25－Polyethylene glycol compound TPA.A high molecular weight compound of a polyethylene glycol and a diepoxide as Carbowax 20M-TPA from suppliers of chromatographic reagents.G26－25% 2-Cyanoethyl-75% methylpolysiloxane.G27－5% Phenyl-95% methylpolysiloxane.G28－25% Phenyl-75% methylpolysiloxane.G29－3,3’-Thiodipropionitrile.G30－Tetraethylene glycol dimethyl ether.G31－Nonylphenoxypoly(ethyleneoxy)ethanol (av.ethyleneoxy chain length is 30);Nonoxynol 30.G32－20% Phenylmethyl-80% dimethylpolysiloxane.G33－20% Carborane-80% methylsilicone.G34－Diethylene glycol succinate polyester stabilized with phosphoric acid.G35－A high molecular weight compound of a polyethylene glycol and a diepoxide that is esterified with nitroterephthalic acid.G36－1% Vinyl-5% phenylmethylpolysiloxane.G37－Polyimide.G38－Phase G1 containing a small percentage of a tailing inhibitor.19G39－Polyethylene glycol(av.mol.wt.about 1500).G40－Ethylene glycol adipate.G41－Phenylmethyldimethylsilicone(10% phenyl-substituted).G42－35% phenyl-65% dimethylpolysiloxane(percentages refer to molar substitution).G43－6% cyanopropyhenyl-94%dimethylpolysiloxane(percentages refer to molar substitution).G44－2% low molecular weight petrolatum hydrocarbon grease and 1% solution of potassium hydroxide.G45－Divinylbenzene-ethylene glycol-dimethylacrylate.G46－14% Cyanopropylphenyl-86% methylpolysiloxane.G47－Polvethylene glycol(av.mol.wt.of about 8000).G48－Highly polar,partially cross-linked cyanopolysiloxane.G49－Proprietary derivatized phenyl groups on a polysiloxane backbone.20SupportsNOTE－Unless otherwise specified,mesh sizes of 80 to 100or,alternatively,100 to 120 are intended.S1A－Siliceous earth for gas chromatography has been fluxcalcined by mixing diatomite with Na2CO3 flux and calcining above 900°.The siliceous earth is acid-washed ,then water-washed until neutral,but not base-washed.The silieous earth may be silanized by treating with an agent such as dimethyldichlorosilane21 to mask surface silanol groups.S1AB－The siliceous earth as described above is both acid-and base-washed.21S1C－A support prepared from crushed firebrick and calcined or burned with a clay binder above 900°with subsequent acid-wash.It may be silanized.S1NS－The siliceous earth is untreated.S2－Styrene-divinylbenzene copolymer having a nominal surface area of less than50㎡per g and an average pore diameter of 0.3 to 0.4 μm.S3－Copolymer of ethylvinylbenzene and divinylbenzene having a nominal surface ared of 500 to 600 ㎡per g and an average pore diameter of 0.0075μm.S4－Styrene-divinylbenzene copolymer with aromatic-O and –N groups, having a nominal surface area of 400 to 600㎡per g and an average pore diameter of 0.0076μm.S5－40-to60-mesh,high-molecular weight tetrafiuorethylenepolymer.S6－Styrene-divinylbenzene copolymer having a nominal surfasearea of 250 to 350㎡per g and an average pore diameter of 0.0091μm.S7-Graphitized carbon having a nominal surface area of 12㎡per g.S8-Copolymer of 4-vinyl-pyridine and styrene-divinylbenzene.S9-A porous polymer based on 2,6-diphenly-p-phenylene oxide. S10-A highly polar cross-linked copolymer of acrylonitrite and divinylbenzene.S11-Graphitized canbon having a nominal surface area of 100㎡per g modified with small amounts of petrolatum and polyethylene glycol compound,22S12-Graphitized carbon having a nominal surface ared of 100 ㎡per g.。
分子空间构型 英语
分子空间构型英语Molecular Spatial Configurations.Molecular spatial configuration, often referred to as molecular geometry, is a crucial aspect of chemistry that deals with the arrangement of atoms within a molecule. It determines the overall shape of a molecule and plays a significant role in its chemical properties and interactions. Understanding molecular geometry is essential for predicting and explaining various chemical phenomena.The spatial configuration of a molecule is primarily influenced by two factors: the number and types of atoms present and the bonds that hold them together. The bonds between atoms can be covalent, ionic, or metallic, depending on the type of interaction involved. Covalent bonds, which are the focus of this discussion, are formed when two atoms share electrons to achieve a stable electron configuration.In covalent molecules, the geometry is primarily determined by the electron pair distribution around the central atom. This distribution is influenced by the number of electron pairs (both bonding and non-bonding) and the presence of any lone pairs, which are electron pairs not involved in bonding. Lone pairs occupy more space than bonding pairs and, therefore, have a significant impact on the overall shape of the molecule.There are several common molecular geometries encountered in chemistry, each with its unique characteristics and properties. One of the most basic geometries is the linear configuration, observed in molecules such as carbon dioxide (CO2). In this geometry, the atoms are arranged in a straight line with a bond angle of 180°, and the central atom has no lone pairs.Another common geometry is the trigonal planar configuration, which is seen in molecules like water (H2O). In this case, the central atom is surrounded by three other atoms, forming a triangular plane with bond angles of approximately 120°. However, it's important to note thatthe presence of lone pairs on the central atom can distort this geometry, leading to a tetrahedral or bent configuration.The tetrahedral geometry is another widely encountered configuration, exemplified by methane (CH4). In this geometry, the central atom is surrounded by four other atoms, forming a tetrahedron with bond angles of approximately 109.5°. This geometry is also common in molecules with a central atom having four bonding pairs and no lone pairs.In addition to these basic geometries, there are more complex configurations such as trigonal bipyramidal and octahedral. The trigonal bipyramidal geometry is observed when a central atom is surrounded by five atoms, with three atoms in a planar triangle and two atoms above and below this plane. This geometry is seen in molecules like phosphorus pentachloride (PCl5).The octahedral geometry, on the other hand, is found when a central atom is surrounded by six atoms, forming anoctahedron. This geometry is common in molecules likesulfur hexafluoride (SF6), where the central atom has no lone pairs and is surrounded by six bonding pairs.The study of molecular spatial configurations is not just limited to understanding the shapes of molecules. It also plays a crucial role in predicting the physical and chemical properties of molecules. For example, the polarity of a molecule, which determines its solubility and interaction with other molecules, is influenced by its geometry. Molecules with asymmetric geometries tend to be polar, while those with symmetric geometries are non-polar.Moreover, the geometry of a molecule affects its reactivity and the way it interacts with other molecules. The availability of reactive sites, or the regions where chemical reactions are most likely to occur, is influenced by the spatial arrangement of atoms. Understanding these geometries can help scientists predict and control chemical reactions, leading to the development of new materials, drugs, and other useful compounds.In conclusion, molecular spatial configuration is a fundamental aspect of chemistry that governs the arrangement of atoms within a molecule. It determines the overall shape of a molecule and plays a crucial role in its chemical properties and interactions. By understanding and analyzing these geometries, scientists can gain valuable insights into the behavior of molecules and use this knowledge to design new compounds and materials with desired properties.。
金属晶体、离子晶体、分子晶体、共价晶体的熔点比大小
金属晶体、离子晶体、分子晶体、共价晶体的熔点比大小The melting points of different types of crystals, such as metal, ionic, molecular, and covalent crystals, can vary widely due to the differences in their chemical bonding and structure.Metal crystals generally have high melting points. This is because metallic bonding involves a "sea of electrons" that hold the metal ions together. The strong electrostatic attraction between the positive metal ions and the delocalized electrons leads to a high melting point. Additionally, metals often have closely packed structures that contribute to their strength and stability, further increasing their melting points.金属晶体通常具有较高的熔点。
这是因为金属键中存在着一个“电子海”，它将金属离子聚集在一起。
正电性金属离子与未定位电子之间的强静电相互作用导致了较高的熔点。
金属通常具有紧密堆积的结构，进一步增加了它们的熔点。
Ionic crystals also tend to have high melting points. Ionic bonding involves the transfer of electrons from one atom to another, resulting in the formation of cations (positively charged) and anions (negatively charged). The strong electrostatic attractions between oppositely charged ions contribute to the stability of ionic crystals and result in high melting points.离子晶体也往往具有较高的熔点。
非金属元素构成的单质中一定存在共价键
非金属元素构成的单质中一定存在共价键There are covalent bonds in compounds composed of non-metal elements. This is because non-metals have a strong tendency to gain or share electrons in order to achieve a stable electron configuration. By forming covalent bonds, non-metal atoms can achieve this stability by sharing pairs of electrons with other atoms.在由非金属元素构成的化合物中，存在着共价键。
这是因为非金属元素具有强烈的倾向，希望通过获得或共享电子来达到稳定的电子排布。
通过形成共价键，非金属原子可以与其他原子共享一对电子以实现稳定。
Covalent bonds are formed between two non-metal atoms when they both have a high electronegativity and similar electron affinities. Electronegativity is the ability of an atom to attract electrons towards itself, and electron affinity is the likelihood of an atom gaining an additional electron. In covalent bonding, atoms share electrons and form a stable molecule.当两个非金属原子具有较高的电负性和相似的电子亲和力时，它们之间会形成共价键。
原子间的结合键
结合键类型 离子键
实例
LiCl NaCl KCl RbCl 金刚石 Si Ge Sn Li Na K Rb Ne Ar H2O HF
结合能 ev/mol 主要特征
8.63 7.94 7.20 6.90 1.37 1.68 3.87 3.11 1.63 1.11 0.931 0.852 0.020 0.078 0.52 0.30 无方向性，高配 位数，低温不导 电，高温离子导 电 方向性，低配位 数，纯金属低温 导电率很小 无方向性，高配 位数，密度高， 导电性高，塑性 好 低熔点、沸点压 缩系数大，保留 分子性质 结合力高于无氢 键分子
共价键
金属键类、碱类和金属氧化物主要以离 子键的方式结合。离子键键合的基本特点是以 离子而不是以原子为结合单元。 一般离子晶体中正负离子静电引力较强， 结合牢固。因此。其熔点和硬度均较高。另外， 在离子晶体中很难产生自由运动的电子，因此， 它们都是良好的电绝缘体。但当处在高温熔融 状态时，正负离子在外电场作用下可以自由运 动，即呈现离子导电性
2： 共价键 共价键的实质就是两个或多个电负性相差 不大的原子间通过共用电子对而形成的化学键。 共价键键合的基本特点是核外电子云达到最大 的重叠，形成“共用电子对”，有确定的方位， 且配位数较小。 共价键的结合极为牢固，故 共价晶体具有结构稳定、熔点高、质硬脆等特 点。共价形成的材料一般是绝缘体，其导电性 能差。
写有关化学课的英语作文
写有关化学课的英语作文English Answer:Chemistry is the study of matter and its properties. It is a vast field that encompasses everything from the smallest subatomic particles to the largest molecules and materials. Chemistry is essential to our understanding of the world around us and plays a vital role in many industries, including medicine, agriculture, and manufacturing.One of the most important aspects of chemistry is the periodic table. The periodic table is a tabular arrangement of the chemical elements, organized by their atomic number, electron configuration, and recurring chemical properties. It is a powerful tool that allows chemists to predict the properties of elements and to understand how they will react with each other.Another important aspect of chemistry is chemicalbonding. Chemical bonding is the process by which atoms or ions are held together to form molecules and compounds. There are three main types of chemical bonding: ionic bonding, covalent bonding, and metallic bonding. Ionic bonding occurs when one atom transfers electrons to another atom, resulting in the formation of ions. Covalent bonding occurs when two atoms share electrons to form a covalent bond. Metallic bonding occurs when metal atoms share their valence electrons to form a sea of electrons.Chemistry is a challenging but rewarding subject. It requires a strong foundation in math and physics, as well as a good understanding of the scientific method. However, the rewards of studying chemistry are great. Chemistry can open doors to a wide range of careers in science, medicine, and engineering.中文回答：化学是什么？化学是一门研究物质及其性质的学科。
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Studio 4b: Shape sorter11) Determine molecular geometry based only on rules of nature2) Illustrate how atoms and lone pairs interact with one another3) Visualize the three dimensional arrangement of atoms in covalent structuresReading: VSEPR 9.1-9.2 p 384-397Groups: A Reporter; B Leader; C RecorderQuestion: Do Lewis structures tell all?Data/Fact GatheringLewis structures provide a great deal of useful information about molecules. However, the structures do not provide a three dimensional picture of the molecule. The shape and geometry of molecules are very important in studying chemical reactions. Reactions that take place in living systems, for instance, are very sensitive to molecular shape. Symmetry is one of the common trends observed in shapes in nature. Natural shape symmetry is illustrated in Figure 1.Another important trend in nature is that like forces repel each other. Therefore, electrons align themselves as far apart as possible. Lone pairs are not confined to a bond and therefore they spread out and take up more space – they are bulky.Creating a ModelYou will predict the three dimensional geometry of a series of molecules using three simple rules (also know as VSEPR or valence-shell electron-pair repulsion model):1)Nature loves symmetry! (equal bond lengths and angles)2)Electrons like to be as far apart from each other as possible without disrupting thesymmetry too drastically.3)And, lone pairs take up more space because they are not confined by bonds.1Taken directly from NC State’s Scale-up chemistry (/)3 large spheres (central atom) 3 medium spheres (lone pairs) 9 small spheres (atoms bonded to central atom) 12 toothpicks (bonds)ProtractorThe “3” Electron Pair Geometry1)Draw the Lewis Structures for borane (BH3), and nitrite (NO2- ) in the space provided on the data sheet on the next page.2)Build the two structures described below. Do not disassemble the structures you will be presenting to the class.a) Borane (BH3)3.Insert the toothpicks into 3 small spheres, which represent hydrogens. A large sphererepresents a boron atom. Insert the hydrogen toothpicks around the boron atom. Remember to follow the model rules! Draw your structure in the space provided on the data sheet.4.Once an appropriate structure is obtained, use the protractor to measure the angle betweenthe bonds and record it on the data sheet. If necessary, remove one of the spheres to get a correct measurement.b) Nitrite (NO2-)e a large sphere to represent nitrogen, a medium sphere to represent a lone pair ofelectrons, and two small spheres for oxygens. Build the structure remembering the rules.Draw your structure on the data sheet.4.Measure the angle between the two oxygen atoms (O-N-O bond angle). Record the angle onthe data sheet.5) Each of these molecules have the same electron-pair geometry as they all have three groups of electrons (a pair shared with another atom or a lone pair) around the central atom. What would you name this geometry?6) Each of these molecules has a unique molecular geometry (look only at the atoms around the central atom and not lone pairs.) What would you name each?NitriteLewis Structure Lewis Structure 3-D Structure3-D StructureThe “4” Electron Pair Geometry7)Draw the Lewis Structures for methane (CH4), ammonia (NH3), and water (H2O) in the space provided on the data sheet on the next page.8)Build the three structures described below. Do not disassemble the structure/s you will be presenting to the class.a) Methane (CH4)9.Insert the toothpicks into 4 small spheres, which represent hydrogen atoms. A large sphererepresents a carbon atom. Insert the hydrogen toothpicks around the carbon atom.Remember to follow the model rules! Draw your structure in the space provided on the data sheet.10.Once an appropriate structure is obtained, use the protractor to measure the angles betweentwo hydrogen atoms (H-C-H bond angle). Record the angle/s on the data sheet. You may need to remove one of the spheres to get a correct measurement.Ammonia (NH3)e a large sphere to represent a nitrogen atom, a medium sphere to represent a lone pair ofelectrons, and three small spheres for hydrogen atoms. Build the structure remembering the rules. Draw your structure on the data sheet.10.Measure the angle/s between two hydrogen atoms (H-N-H bond angle). Record the angle/son the data sheet. If necessary, remove one of the spheres to get a correct measurement.Water (H2O)e a large sphere to represent an oxygen atom, two medium spheres to represent the lonepairs and two small spheres to represent the hydrogen atoms. Build and draw the structure.10.Measure the angle between the hydrogen atoms (H-O-H). If necessary, remove one of thespheres to get a correct measurement.11) All of these molecules have the same electron-pair geometry. What would you name thisgeometry.12) Each of these molecules has a unique molecular geometry (look only at the atoms around the central atom and not lone pairs.) What would you name each?AmmoniaWaterLewis Structure Lewis Structure Lewis Structure 3-D Structure3-D Structure3-D Structure13) Should all of the angles in methane be equal? Why or why not?14) In ammonia, which angle should be larger, LP-N-H or H-N-H? Why?15) In water, which angle should be smaller, LP-O-H or LP-O-LP? Why?____________________________________________________STOP HERE!!!The “5” Electron Pair Geometry16)Draw the Lewis Structures for phosphorous pentachloride (PCl5), sulfur tetrafluoride (SF4), bromine trifluoride (BrF3) and xenon difluoride (XeF2 ) on the data sheet on the next page.17)Build the three structures described below. You may need to disassemble some structures to build others.a) Phosphorous pentachloride (PCl5)18.Insert the toothpicks into five small spheres, which represent chlorine atoms. A large sphererepresents a phosphorous atom. Insert the chlorine toothpicks around the carbon atom.Remember to follow the model rules!Hint: Start with the “3” electron pair geometry and then add the other two chlorine atoms. Draw your structure in the space provided on the data sheet.19.Once an appropriate structure is obtained, use the protractor to measure the angle/s betweenthe chlorine atoms and record it/them on the data sheet. If necessary, remove one of thespheres to get a correct measurement.b) Sulfur tetrafluoride (SF4)e a large sphere to represent a sulfur atom, a medium sphere to represent a lone pair ofelectrons, and four small spheres for fluorine atoms. Build the structure remembering the rules. Draw your structure on the data sheet.19.Measure the angle/s between two fluorine atoms (F-S-F bond angle). Record the angle/s onthe data sheet. If necessary, remove one of the spheres to get a correct measurement.c) Bromine trifluoride (BrF3)e a large sphere to represent a bromine atom, two medium spheres to represent the lonepair of electrons and three small spheres to represent the fluorine atoms. Build and draw the structure.19.Measure the angle/s between the fluorine atoms (F-Br-F). If necessary, remove one of thespheres to get a correct measurement.d) Xenon difluoride (XeF2 )e a large sphere to represent a xenon atom, thee medium spheres to represent the lone pairsof electrons and two small spheres to represent fluorine atoms. Build and draw the structure.19.Measure the angle/s between the fluorine atoms (F-Xe-F). If necessary, remove one of thespheres to get a correct measurement.20) Propose names for the electron pair and molecular geometries.Phosphorous pentachlorideSulfur tetrafluorideBromine trifluorideXenon difluorideLewis Structure Lewis StructureLewis Structure3-D Structure3-D Structure3-D StructureLewis Structure 3-D StructureThe “6” Electron Pair Geometry21)Draw the Lewis Structures for sulfur hexafluoride (SF6), bromine pentafluoride (BrF5), and xenon tetrafluoride (XeF4 ) in the space provided on the data sheet on the next page.22)Build the three structures described below. You may need to disassemble some structures to build others.a) Sulfur hexafluoride (SF6)e a large sphere to represent a sulfur atom and six small spheres for fluorine atoms. Buildthe structure remembering the rules. Draw your structure on the data sheet.24.Measure the angle/s between two fluorine atoms (F-S-F bond angle). Record the angle/s onthe data sheet.c) Bromine pentafluoride (BrF5)e a large sphere to represent a bromine atom, one medium sphere to represent the lone pairof electrons and five small spheres to represent the fluorine atoms. Build and draw thestructure.23..Measure the angle/s between two fluorine atoms (F-Br-F bond angle). Record the angle/s onthe data sheet.d) Xenon tetrafluoride (XeF4 )e a large sphere to represent xenon atom, two medium spheres to represent the lone pairsof electrons and four small spheres to represent the fluorine atoms. Build and draw thestructure.24. Measure the angle/s between two fluorine atoms (F-Xe-F bond angle). Record the angle/s onthe data sheet.25) Propose names for the electron pair and molecular geometries.Sulfur hexafluorideBromine pentafluorideXenon tetrafluorideLewis Structure Lewis Structure 3-D Structure3-D StructureLewis Structure3-D Structure。