IGCSE CIE Chemistry: Chemical Bonding Key Points | IGCSE CIE 化学：化学键 考点精讲

📚 IGCSE CIE Chemistry: Chemical Bonding Key Points | IGCSE CIE 化学：化学键 考点精讲

Chemical bonding is the force that holds atoms together in compounds and elements. Understanding the three main types of bonding – ionic, covalent and metallic – is crucial for IGCSE Chemistry. This article covers key exam points, including structure, properties and dot-and-cross diagrams.

化学键是使原子结合成化合物和单质的作用力。理解离子键、共价键和金属键这三种主要键型对 IGCSE 化学至关重要。本文涵盖结构、性质和点叉图等核心考点。

1. Introduction to Chemical Bonding | 化学键简介

Atoms bond to achieve a stable electron configuration, usually a full outer shell (octet rule). The type of bonding depends on whether electrons are transferred, shared or delocalised.

原子通过成键达到稳定的电子构型，通常是满的外层（八隅体规则）。成键类型取决于电子是转移、共用还是离域。

Metals tend to lose electrons to form cations, while non-metals tend to gain electrons to form anions. Noble gases are unreactive because they already have full outer shells.

金属容易失去电子形成阳离子，而非金属容易得到电子形成阴离子。稀有气体不活泼，因为它们已经拥有满的外层电子。

2. Ionic Bonding: Electron Transfer | 离子键：电子转移

Ionic bonding occurs between a metal and a non-metal. The metal atom loses one or more electrons to become a positively charged cation, while the non-metal atom gains those electrons to become a negatively charged anion.

离子键发生在金属和非金属之间。金属原子失去一个或多个电子成为带正电的阳离子，非金属原子得到那些电子成为带负电的阴离子。

The oppositely charged ions are held together by strong electrostatic forces of attraction, forming a giant ionic lattice.

带相反电荷的离子通过强大的静电吸引力结合在一起，形成巨型离子晶格。

Example: Sodium chloride (NaCl). Sodium (2,8,1) loses one electron to become Na⁺ (2,8), while chlorine (2,8,7) gains one electron to become Cl⁻ (2,8,8). The overall formula is NaCl.

例如：氯化钠 (NaCl)。钠 (2,8,1) 失去一个电子变成 Na⁺ (2,8)，氯 (2,8,7) 得到一个电子变成 Cl⁻ (2,8,8)。总化学式为 NaCl。

Na → Na⁺ + e⁻ ； Cl + e⁻ → Cl⁻

3. Properties of Ionic Compounds | 离子化合物的性质

Ionic compounds have high melting and boiling points because a large amount of energy is needed to overcome the strong electrostatic forces between ions in the giant lattice.

离子化合物具有高熔点和沸点，因为需要大量能量来克服巨型晶格中离子间的强静电吸引力。

They do not conduct electricity when solid, because the ions are fixed in position and cannot move. However, when molten or dissolved in water, the ions are free to move and can conduct electricity.

它们在固态时不导电，因为离子固定在晶格位置上无法移动。但熔融或溶于水时，离子可以自由移动，因此能够导电。

Many ionic compounds are soluble in water. The ions separate and become surrounded by water molecules.

许多离子化合物可溶于水。离子分离并被水分子包围。

They are usually hard and brittle. When a force is applied, layers of ions shift and like charges align, causing repulsion and shattering.

它们通常坚硬而脆。施加外力时，离子层滑动，同性电荷相对，产生排斥导致碎裂。

4. Covalent Bonding: Sharing Electrons | 共价键：共用电子

Covalent bonding occurs between non-metal atoms. Atoms share one or more pairs of electrons to achieve a full outer shell. The shared pair is attracted to the nuclei of both atoms, holding them together.

共价键发生在非金属原子之间。原子共用一对或多对电子以达到满外层。共用电子对同时被两个原子核吸引，将它们结合在一起。

A single covalent bond involves one shared pair of electrons (e.g., H₂, Cl₂). A double bond involves two shared pairs (e.g., O=O in O₂), and a triple bond involves three shared pairs (e.g., N≡N in N₂).

单键共用一对电子（如 H₂, Cl₂）；双键共用两对电子（如 O₂ 中的 O=O）；三键共用三对电子（如 N₂ 中的 N≡N）。

In a molecule, the atoms are held together by strong covalent bonds, but the intermolecular forces between molecules are weak.

分子内原子由强的共价键连接，但分子之间的分子间作用力较弱。

Simple covalent compounds include H₂O, CO₂, NH₃, CH₄. The bonds are within the molecule, not between molecules.

简单共价化合物包括 H₂O、CO₂

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