Edexcel A-Level Chemistry: Atomic Structure and the Periodic Table | 原子结构与元素周期表

📚 Edexcel A-Level Chemistry: Atomic Structure and the Periodic Table | 原子结构与元素周期表

Understanding atomic structure is the foundation of A-Level Chemistry. This revision article reviews the particles in the atom, isotopes, mass spectrometry, electron arrangement, ionisation energy and periodic trends for Edexcel A-Level candidates.

理解原子结构是 A-Level 化学的基础。本篇复习文章为 Edexcel A-Level 考生梳理原子中的粒子、同位素、质谱、电子排布、电离能以及周期趋势。

1. Subatomic Particles and Their Properties | 亚原子粒子及其性质

Atoms contain three subatomic particles: protons, neutrons and electrons. Protons and neutrons are found in the dense central nucleus, while electrons occupy orbitals around the nucleus.

原子包含三种亚原子粒子：质子、中子和电子。质子和中子位于致密的中心原子核内，而电子占据原子核外的轨道。

The relative charges and masses of these particles are summarised below. The electron has a very small mass compared with the proton and neutron, so most of the mass of an atom is concentrated in the nucleus.

这些粒子的相对电荷和相对质量总结如下。电子的质量与质子和中子相比非常小，因此原子的大部分质量集中在原子核内。

In an atom, the number of protons equals the number of electrons, so atoms have no overall charge. The proton number defines the element.

在原子中，质子数等于电子数，因此原子整体不带电。质子数决定了元素的种类。

2. Atomic Number and Mass Number | 原子序数与质量数

The atomic number, Z, is the number of protons in the nucleus. It identifies the element and determines its position in the periodic table. The mass number, A, is the total number of protons plus neutrons in the nucleus.

原子序数 Z 是原子核内的质子数。它确定了元素的种类及其在周期表中的位置。质量数 A 是原子核内质子数与中子数之和。

For a neutral atom, the number of electrons is also equal to Z. The number of neutrons, N, is found using the relationship:

对于中性原子，电子数也等于 Z。中子数 N 可通过以下关系式求出：

A = Z + N

For example, ¹²₆C has 6 protons, 6 electrons and 6 neutrons. ¹⁴₆C has the same number of protons and electrons but 8 neutrons.

例如，¹²₆C 有 6 个质子、6 个电子和 6 个中子。¹⁴₆C 具有相同的质子数和电子数，但有 8 个中子。

3. Isotopes and Relative Atomic Mass | 同位素与相对原子质量

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. They have the same atomic number but different mass numbers.

同位素是同一元素中质子数相同但中子数不同的原子。它们的原子序数相同，但质量数不同。

Because isotopes have different masses, the average mass of an element is calculated from the abundance of each isotope. The relative atomic mass, Aᵣ, is given by:

由于同位素的质量不同，元素的平均质量由各同位素的丰度计算得出。相对原子质量 Aᵣ 的计算公式为：

Aᵣ = Σ (isotopic mass × percentage abundance)