Core Theory for CAIE IGCSE Chemistry 0620 | CAIE IGCSE 化学 0620 核心理论

📚 Core Theory for CAIE IGCSE Chemistry 0620 | CAIE IGCSE 化学 0620 核心理论

This article summarises the essential theory topics in the CAIE IGCSE Chemistry 0620 syllabus. It is designed to help you revise key definitions, patterns and calculations before the examination.

本文总结 CAIE IGCSE 化学 0620 课程的核心理论主题，旨在帮助你复习关键定义、规律和计算，为考试做好准备。

1. Atomic Structure and Isotopes | 原子结构与同位素

An atom consists of a central nucleus containing protons and neutrons, surrounded by electrons arranged in shells. Protons carry a positive charge, electrons carry a negative charge, and neutrons are neutral. The proton number (atomic number) determines the element, while the nucleon number (mass number) equals the total number of protons plus neutrons.

原子由含质子和中子的中心原子核以及按电子层排列的核外电子组成。质子带正电荷，电子带负电荷，中子不带电。质子数（原子序数）决定元素种类，而核子数（质量数）等于质子数与中子数之和。

Isotopes are atoms of the same element with the same proton number but different nucleon numbers. They have identical chemical properties because they have the same number of outer-shell electrons, but different physical properties such as mass.

同位素是同一元素中质子数相同但核子数不同的原子。它们的化学性质相同，因为外层电子数相同，但质量等物理性质不同。

Relative atomic mass Aᵣ = (Σ isotope mass × percentage abundance) / 100

相对原子质量 Aᵣ = (Σ 同位素质量 × 百分丰度) / 100

Electrons occupy shells with maximum capacities of 2, 8, 8 for the first three shells in IGCSE. The electronic configuration controls the element’s group and period in the Periodic Table.

电子占据电子层，IGCSE 阶段前三层最多容纳 2、8、8 个电子。电子排布决定元素在周期表中的族和周期。

2. Ionic Bonding | 离子键

Ionic bonding occurs when a metal atom transfers one or more electrons to a non-metal atom. The metal forms a positive cation, and the non-metal forms a negative anion. Oppositely charged ions attract each other strongly in a giant ionic lattice.

当金属原子将一个或多个电子转移给非金属原子时，形成离子键

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