📚 IGCSE AQA Chemistry: Chemical Bonding Key Points | IGCSE AQA 化学：化学键 考点精讲
Welcome to this comprehensive revision guide on Chemical Bonding for the IGCSE AQA Chemistry specification. Here we will break down the key concepts, from ionic and covalent bonding to metallic structures, and link them to typical exam questions. Mastering chemical bonding is essential for understanding the properties of substances and scoring high marks on your IGCSE paper.
欢迎来到IGCSE AQA化学化学键考点精讲。我们将分解关键概念，从离子键、共价键到金属结构，并将它们与典型考题联系起来。掌握化学键对于理解物质的性质以及在IGCSE考试中取得高分至关重要。
1. Understanding Chemical Bonding | 理解化学键
Atoms bond together to achieve a full outer shell of electrons, becoming more stable. This is known as the octet rule: atoms tend to gain, lose or share electrons to attain the electron configuration of a noble gas. The driving force is a lower energy state.
原子通过键合来获得满外电子层，变得更加稳定。这叫做八隅体规则：原子倾向于得到、失去或共享电子，以达到稀有气体的电子构型。驱动力是达到更低的能量状态。
There are three main types of chemical bonding: ionic, covalent and metallic. The type of bonding depends on the elements involved and their electronegativities. In IGCSE, you will be expected to identify the bonding type from the elements present.
化学键主要有三种类型：离子键、共价键和金属键。键的类型取决于涉及的元素及其电负性。在IGCSE中，你需要能够根据所含元素来识别键的类型。
2. Formation of Ions | 离子的形成
Ions form when atoms gain or lose electrons. Metals lose electrons to form positive ions (cations), while non-metals gain electrons to form negative ions (anions). The number of electrons lost or gained is determined by the element's group number.
离子是原子得到或失去电子而形成的。金属失去电子形成阳离子（正离子），非金属得到电子形成阴离子（负离子）。失去或得到的电子数取决于元素的族数。
For example, sodium (Group 1) loses one electron to form Na⁺; magnesium (Group 2) loses two electrons to form Mg²⁺. Chlorine (Group 7) gains one electron to form Cl⁻, and oxygen (Group 6) gains two electrons to form O²⁻. Transition metals can form ions with different charges, such as Fe²⁺ and Fe³⁺, but at IGCSE focus is on Groups 1, 2, 6 and 7.
例如，钠（第1族）失去一个电子形成 Na⁺；镁（第2族）失去两个电子形成 Mg²⁺。氯（第7族）得到一个电子形成 Cl⁻，氧（第6族）得到两个电子形成 O²⁻。过渡金属可以形成不同电荷的离子，如 Fe²⁺ 和 Fe³⁺，但在IGCSE中重点关注第1、2、6和7族。
Na → Na⁺ + e⁻ ; Cl + e⁻ → Cl⁻
3. Ionic Bonding | 离子键
Ionic bonding occurs between a metal and a non-metal. The metal atom transfers electrons to the non-metal atom, forming oppositely charged ions. These ions are held together by strong electrostatic forces of attraction, which act in all directions in a giant ionic lattice.
离子键发生在金属和非金属之间。金属原子将电子转移给非金属原子，形成带相反电荷的离子。这些离子通过强静电引力结合在一起，这种引力在巨大离子晶格中作用于所有方向。
The formula of an ionic compound is the simplest ratio of ions that produces an electrically neutral lattice. For sodium chloride, the ratio is 1:1, giving NaCl. For magnesium oxide, Mg²⁺ and O²⁻ combine in a 1:1 ratio, giving MgO. For magnesium chloride, Mg²⁺ needs two Cl⁻ ions, giving MgCl₂.
离子化合物的化学式是产生电中性晶格的最简离子比例。对于氯化钠，比例为 1:1，化学式为 NaCl。对于氧化镁，Mg²⁺ 和 O²⁻ 以 1:1 结合，化学式为 MgO。对于氯化镁，Mg²⁺ 需要两个 Cl⁻，化学式为 MgCl₂。
4. Dot-and-Cross Diagrams for Ionic Compounds | 离子化合物的点交叉图
An ionic dot-and-cross diagram shows the transfer of electrons. Only outer shell electrons are drawn; different symbols (dots and crosses) represent electrons from different atoms. After transfer, the ions are drawn in brackets with their charges.
离子点交叉图显示电子转移。只画最外层电子；用不同的符号（点和叉）表示来自不同原子的电子。转移后，离子用方括号括起来并标明电荷。
For NaCl: Draw sodium atom with one dot in its outer shell, chlorine atom with seven crosses. After transfer, Na⁺ has an empty outer shell (no dots), and Cl⁻ is shown with eight electrons (one dot and seven crosses) inside square brackets with a '⁻' sign. The charges must balance.
对于 NaCl：画出钠原子最外层有一个点，氯原子有七个叉。转移后，Na⁺ 最外层为空（没有点），Cl⁻ 用方括号括起，内部有八个电子（一个点和七个叉），并标上 '⁻' 号。电荷必须平衡。
For ionic compounds containing more than two ions, draw the correct number of each ion. For MgCl₂, one Mg atom loses two electrons, each shown going to a Cl atom. Two chloride ions are formed, each with 8 electrons.
对于含有多于两个离子的离子化合物，要画出正确数量的每种离子。对于 MgCl₂，一个 Mg 原子失去两个电子，每个电子转移给一个 Cl 原子。形成两个氯离子，每个有 8 个电子。
5. Properties of Ionic Compounds | 离子化合物的性质
Ionic compounds have high melting and boiling points because the giant lattice of ions is held together by strong electrostatic forces, requiring a large amount of energy to overcome. They are solid at room temperature.
离子化合物具有高熔点和沸点，因为离子巨大晶格由强静电引力维系，需要大量能量来克服。它们在室温下为固体。
They conduct electricity only when molten (liquid) or dissolved in water. In these states, the ions are free to move and carry charge. In the solid state, the ions are locked in place, so they cannot conduct electricity.
它们仅在熔融态（液态）或溶于水时导电。在这些状态下，离子可以自由移动并携带电荷。在固态下，离子被固定在位置上，因此不能导电。
Many ionic compounds are soluble in water because water molecules can attract and separate the ions. This process is called dissociation.
许多离子化合物可溶于水，因为水分子可以吸引并分离离子。这个过程称为解离。
6. Covalent Bonding | 共价键
Covalent bonding occurs between non-metal atoms. The atoms share one or more pairs of electrons so that each atom can achieve a full outer shell. A shared pair of electrons is a covalent bond.
共价键发生在非金属原子之间。原子共享一对或多对电子，使每个原子都能获得满外电子层。一个共享电子对就是一个共价键。
oup of atoms held together by covalent bonds. Single bonds involve one shared pair (e.g. H–H), double bonds two shared pairs (O=O), and triple bonds three shared pairs (N≡ can form is often linked to the number of electrons it needs to complete its outer shell.
分子是由共价键连接在一起的独立原子团。单键涉及一对共享电子（如 H–H），双键两对共享电子（O=O），三键三对共享电子（N≡N）。一个原子能形成的键数通常与其达到满壳层所需的电子数有关。
7. Dot-and-Cross Diagrams for Simple Molecules | 简单分子的点交叉图
In covalent dot-and-cross diagrams, we show only the outer electron shells. Shared electrons are drawn as a pair of a dot and a cross in the overlap between atoms. Unshared electrons (lone pairs) are also shown.
在共价点交叉图中，我们只显示最外层电子壳层。共享电子被画成位于原子重叠区的一个点和一个叉。未共享电子（孤对电子）也要画出。
Example – Water (H₂O): Oxygen has 6 outer electrons, each hydrogen has 1. Oxygen shares one electron with each hydrogen, forming two O–H single bonds. The remaining four outer electrons on oxygen form two lone pairs.
举例 – 水 (H₂O)：氧有 6 个外层电子，每个氢有 1 个。氧与每个氢各共享一个电子，形成两个 O–H 单键。氧上剩余的四个外层电子形成两对孤对电子。
Example – C=O double bonds. No lone pairs remain on carbon; each oxygen ends up with two lone pairs.
举例 – 二氧化碳 (CO₂)：碳有 4 个外层电子，每个氧有 6 个。碳与每个氧共享两对电子，形成两个 C=O 双键。碳上没有孤对电子；每个氧最终有两对孤对电子。
8. Properties of Simple Molecular Substances | 简单分子物质的性质
Simple molecular substances consist of small molecules. They have low melting and boiling points because the intermolecular forces between molecules are weak compared to covalent bonds. Only a small amount of energy is needed to separate molecules.
简单分子物质由小分子组成。它们具有低熔点和沸点，因为分子间的分子间作用力与共价键相比很弱。分离分子只需要很少的能量。
They do not conduct electricity in any state because there are no free ions or delocalised electrons. All electrons are locked in covalent bonds or lone pairs within the molecules.
它们在任何状态下都不导电，因为没有自由离子或离域电子。所有电子都被固定在分子内的共价键或孤对电子中。
As the size of the molecules increases, the intermolecular forces (van der Waals forces) become stronger, leading to higher boiling points. This explains why larger alkanes have higher boiling points.
随着分子变大，分子间作用力（范德华力）变强，导致沸点升高。这解释了为什么更大的烷烃具有更高的沸点。
9. Giant Covalent Structures | 巨分子共价结构
Some non-metal substances form giant covalent structures (macromolecules) where many atoms are joined by strong covalent bonds in a continuous three-dimensional lattice. The whole structure is essentially one huge molecule.
一些非金属物质形成巨分子共价结构（大分子），许多原子通过强共价键连接成连续的三维晶格。整个结构本质上是一个巨大的分子。
Diamond: Each carbon atom forms four strong covalent bonds in a tetrahedral arrangement. This makes diamond extremely hard, with a very high melting point. It does not conduct electricity because all electrons are used in bonds.
金刚石：每个碳原子以四面体
Published by TutorHao | IGCSE Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图