原子核的基本性质

Isomer (EB)
• in nuclear physics, any of two or more nuclides (species of atomic nuclei) that consist of the same number of protons and the same number of neutrons but differ in energy and manner of radioactive decay, and that exist for a measurable interval of time. • The half-life of the more energetic isomer may be as short as about 10-11 second but, in some extreme cases, as long as several years.
同质异能素(isomer)
• Isomers are the nuclides with the same number of protons and neutrons, but having different energy states. • The excited states are called the isomeric states, which can have a lifetime varying from picoseconds to years.
同量异位素(isobar)
• 质量数相同而质子数不同的核素
例如
40Ar, 40K ,40Ca
• One of two or more isotopes of different elements, with the same atomic weight (Concise Oxford)
• one of two or more atoms or elements having the same atomic weights or mass numbers but different atomic numbers (Merriam-Webster)
原子核的组成、电荷、质量及半径
质子(proton)
• 电荷、质量 • 存在方式 • 发现、命名 • 用途
Proton
• stable subatomic particle that has a positive charge equal in magnitude to a unit of electron charge and a rest mass of 1.67262×10-27 kg, which is 1,836 times the mass of an electron.
• English physicist who received the Nobel Prize for Physics in 1935 for the discovery of the neutron
原子核的中子-质子模型
• 原子序数为Z质量数为A的原子核的组成
• 核子(nucleon)
• 原子核的质子数，中子数与核子数 • 注：原子核的质子-电子模型
Isotope(EB)
• one of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behaviour but with different atomic masses and physical properties.
Nuclide(EB)
• also called nuclear species, species of atom as characterized by the number of protons, the number of neutrons, and the energy state of the nucleus.
第二章 原子核的基本性质
Basic Characteristics of the Atomic Nucleus
目的
• 熟悉原子核的组成
• 了解原子核稳定性的相关因素 • 了解核力的主要性质 • 掌握原子核结合能的概念与计算
内容
• 原子核的组成
• 原子核的稳定性
• 核力的主要性质 • 原子核的结合能
• Every chemical element has one or more isotopes.
同位素丰度(abundance)
• 同位素中各核素天然含量的百分比
例如，天然存在的氧有三种稳定同位素： 16O,17O和18O，它们的同位素丰度分别为 99.757%, 0.038%, 0.205% (IUPAC 2003)
Proton
• The discovery of the proton dates to the earliest investigations of atomic structure. • While studying streams of ionized gaseous atoms and molecules from which electrons had been stripped, Wilhelm Wien (1898) and J.J. Thomson (1910) identified a positive particle equal in mass to the hydrogen atom. • Ernest Rutherford showed (1919) that nitrogen under alpha-particle bombardment ejects what appear to be hydrogen nuclei. • By 1920 he had accepted the hydrogen nucleus as an elementary particle, naming it proton.
Werner Heisenberg
• born Dec. 5, 1901, Wurzburg, Ger. died Feb. 1, 1976, Munich • German physicist and philosopher who discovered a way to formulate quantum mechanics in terms of matrices (1925). For that discovery, he was awarded the Nobel Prize for Physics for 1932. • In 1927 he published his indeterminacy, or uncertainty, principle, upon which he built his philosophy and for which he is best known.
原子核的表示
• 质量数为A，质子数为Z，中子数为N的原 子核的表示
核素(nuclide)
• 具有确定数目的中子和质子的原子核称为核素 • 具有相同质子数和中子数的一类原子核，称为一 种核素。有时也把具有相同原子序数和质量数的 一类原子，称为一种核素（卢希庭） • A certain type of atom characterized by the number of protons and neutrons in its nucleus (Concise Oxford) • a species of atom characterized by the constitution of its nucleus and hence by the number of protons, the number of neutrons, and the energy content (Merriam-Webster)
同质异能素(isomer)
• 激发态寿命较长的原子核称为基态原子核的同质 异能素
• 质量数和质子数均相同，而能量状态不同的核素 称为同核异能素（卢希庭） • One of two or more atomic nuclei that have the same atomic number and the same mass number but different energy states (Concise Oxford)
• 同质异能素这个术语的出现表明，核素还与能量 相关
Leabharlann Baidu
讨论和提问
（1~3分钟）
原子核的电荷
qZ e
• 人类已发现元素的核电荷数
• 超铀元素 • 核电荷数测量方法
原子核的质量
mN M A Zme
• 在一般工作中，如果采用原子质量来代替 原子核的质量进行计算，对计算结果往往 并无多大影响
• When the isomeric states are long-lived, they are referred to as metastable states. These states are denoted by “m” as in 99mTc. (Saha)
核素术语小结
• 同位素、同量异位素、同质异能素等术语表达的 是核素之间的一种关系，而非某个具体的核素 • 核素是包含特定原子核（质子数与中子数一定） 的一类原子的总称，否则，讲“同位素具有相同 的化学性质”便没有意义
(Concise Oxford)
• any of two or more species of atoms of a chemical element with the same atomic number and nearly identical chemical behavior but with differing atomic mass or mass number and different physical properties (Merriam-Webster)
• A nuclide is thus characterized by the mass number (A) and the atomic number (Z).
同位素(isotope)
• 质子数相同而中子数不同的各核素统称为某元素 的同位素（同位素是指各核素在元素周期表中处 于同一个位置，具有相同的化学性质） • 质子数相同，中子数不同的核素称为同位素（卢 希庭） • Chem. One of two or more forms of an element differing from each other in relative atomic mass, and in nuclear but not chemical properties
• 表示原子质量的单位：amu (u), MeV/c2
原子核的半径
r r0 A
• 原子核密度的量级：
1
3
• 原子核半径参数r0：1.1(1.2)fm（核电荷分 布）， 1.4~1.5fm（核力作用） 1014 g/cm3
讨论和提问
Isotopic abundance
• Isotopic abundances refer to the relative proportions of the stable isotopes of each element. • They are most often quoted as atom percentages
中子(neutron)
• 电荷、质量 • 存在方式 • 发现: 9Be(α,n)12C
• 用途 • 稳定性
James Chadwick
• born Oct. 20, 1891, Manchester, Eng. died July 24, 1974, Cambridge, Cambridgeshire