Edexcel A-Level Combined Science: Topic 105 – Atomic Structure and the Periodic Table | Edexcel A-Level 综合科学：专题 105 – 原子结构与元素周期表

📚 Edexcel A-Level Combined Science: Topic 105 – Atomic Structure and the Periodic Table | Edexcel A-Level 综合科学：专题 105 – 原子结构与元素周期表

Atomic structure is the foundation of all chemical and physical behaviour. In Edexcel A-Level Combined Science, Topic 105 requires you to link subatomic particles, electron configurations, ionisation energies and periodic trends. This guide walks through the key ideas, worked comparisons and common exam traps.

原子结构是所有化学与物理行为的基础。在 Edexcel A-Level 综合科学中，专题 105 要求你把亚原子粒子、电子排布、电离能和周期趋势联系起来。本指南将梳理核心概念、典型对比和常见考试陷阱。

1. Subatomic Particles and Nuclear Symbols | 亚原子粒子与核素符号

Atoms contain three main subatomic particles. Protons have a relative charge of +1 and a relative mass of 1. Neutrons have a relative charge of 0 and a relative mass of 1. Electrons have a relative charge of -1 and a relative mass of 1/1836. The nucleus contains virtually all the mass but occupies a tiny fraction of the atomic volume.

原子包含三种主要亚原子粒子。质子相对电荷为 +1，相对质量约为 1；中子相对电荷为 0，相对质量约为 1；电子相对电荷为 -1，相对质量约为 1/1836。原子核几乎集中了全部质量，但只占原子体积的极小部分。

The atomic number Z is the number of protons. The mass number A is the total number of protons and neutrons. In a neutral atom the number of electrons equals the number of protons, so the charges balance. When an atom loses or gains electrons it forms a positive or negative ion.

原子序数 Z 是质子数。质量数 A 是质子与中子总数。中性原子的电子数等于质子数，因此电荷平衡。当原子失去或得到电子时，会形成正离子或负离子。

^A_ZX

A = Z + n

The symbol n stands for the number of neutrons. You must be able to read and write these nuclear symbols, for example ¹²₆C means an atom of carbon with 6 protons and 6 neutrons.

符号 n 表示中子数。你必须能读、能写核素符号，例如 ¹²₆C 表示一个质子数为 6、中子数为

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