专业英语课件 3

negative in sign for electrons and positive for protons;
neutrons are electrically neutral.
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电子百度文库
Ⅰ- ATOMIC STRUCTURE
2.1 FUNDAMENTAL CONCEPTS
• Masses for these subatomic particles are infinitesimally (Immeasurably or incalculably minute) small; protons and neutrons have approximately (about) the same mass, 1.67× 10-27 kg, which is significantly larger than that of an electron, 9.11 × 10-31 kg.
• These topics are reviewed briefly, under the assumption that some of the material is familiar to the reader.
What should you be able to do after studying this chapter?
s轨道
p轨道
d轨道
（3）Magnetic quantum number
The third quantum number describes the number of energy states for each subshell, which is restricted by 2l+1.
E.g. l＝1，ml 可以为 0，1三个不同的取向，用px, py, pz 表示。 l＝2, ml 可以为 0，1 , 2, 五个不同的取向，用dxy, dyz, dxz, dx2-y2, dz2表示。
Introduction
• Some of the important properties of solid materials depend on geometrical atomic arrangements, and also the interactions that exist among constituent (component) atoms or molecules. This chapter, by way of preparation for subsequent discussions, considers several fundamental and important concepts, namely: atomic structure, electron configurations in atoms and the periodic table, and the various types of primary and secondary interatomic bonds that hold together the atoms comprising (consisting of ) a solid.
Why study atomic structure and interatomic
bonding?
• An important reason to have an understanding of interatomic bonding in solids is that, in some instances, the type of bond allows us to explain a material’s properties.
• Each chemical element is characterized by the number of protons in the nucleus, or the atomic number (Z).
• The atomic mass (A) of a specific atom may be expressed as the sum of the masses of protons and neutrons within the nucleus.
Name and explain the primary or chemical bond found in solids.
ATOMIC STRUCTURE
• 2.1 FUNDAMENTAL CONCEPTS
• Each atom consists of a very small nucleus（pl. nuclei ） composed of protons and neutrons, which is
Technical English
Atomic Structure and Interatomic Bonding
Covalent Bond(SiO2 B2O3)
Metallic bond
Learning Objectives
1. Name the two atomic models cited, and note the differences between them.
2. Describe the important quantum-mechanical principle that relates to electron energies.
3. (a) Briefly describe ionic, covalent, metallic, hydrogen, and van der Waals bonds. (b) Note what materials exhibit each of these bonding types.
2.2 Electrons in ATOMS
Atomic models
➢ 1. One early outgrowth of quantum mechanics was the simplified Bohr atomic model, in which electrons are assumed to resolve around the atomic nucleus in discrete orbitals, but the position of any particular electron is more or less well defined in terms of its orbital.
(2) Angular Quantum Number
The number of these subshells is restricted by the magnitude of n.
The subshell is denoted by a lowercase letter- an s, p, d, f, which is related to the shape of the electron subshell.
encircled原(e子n核compassed) by moving electrons.
• Both electrons and protons are electrically charged, the
charge magnitude being 1.60 × 10-19 C, which is
• All the elements have been classified according to electron configuration in the periodic table
• For example, consider carbon, which may exist as both graphite and diamond. Whereas graphite is relatively soft and has a ‘‘greasy’’ feel to it, diamond is the hardest known material.
• Although the number of protons is the same for all atoms of a given element, the number of neutrons (N) may be variable（changeable）.
• Thus atoms of some elements have two or more different atomic masses, which are called isotopes.
2.2 Electrons in ATOMS
Atomic models
➢ 2. Another quantummechanical principle stipulates that the energies of electrons are quantized. An electron may change energy. It is convenient to think of these allowed electron energies as being associated with energy levels or states.
e.g. The number of available electron states in some of the electron shells and subshells
Ⅱ- THE PERIODIC TABLE
The electronegativity value for the elements
Pauling近似能级图
(1) Principal Quantum number
These shells are designated by n=1,2,3…, which correspond, respectively, to the letters K,L,M….
The quantum number is related to the distance of an electron from the nucleus or its position.
（4）Spin quantum number
Associated with each electron is a spin moment, which must be oriented either up or down, for which two values are possible (±1/2)
• This dramatic (significant) disparity (difference) in properties is directly attributable to a type of interatomic bonding found in graphite that does not exist in diamond
This micrograph, which represents the surface of a gold specimen, was taken with a sophisticated （complex）atomic force microscope (AFM). Individual atoms for this (111) crystallographic surface plane are resolved. Also note the dimensional scale (in the nanometer range) below the micrograph.
Pauling近似能级图
2.2 Electrons in ATOMS
Quantum numbers
Using wave mechanics, every electron in an atom is characterized by four parameters called quantum numbers.