Unit 4 Year 9 Chemistry Homework: Chemical Bonding and Structure (pp. 69-91) | 第4单元九年级化学作业：化学键合与结构（第69-91页）

📚 Unit 4 Year 9 Chemistry Homework: Chemical Bonding and Structure (pp. 69-91) | 第4单元九年级化学作业：化学键合与结构（第69-91页）

This article covers the core ideas in Unit 4 pages 69-91 for Year 9 Chemistry homework. The focus is on how atoms bond, why different structures form, and how bonding explains the properties of substances.

本文覆盖九年级化学作业第4单元第69-91页的核心内容。重点在于原子如何键合、为何形成不同结构，以及键合如何解释物质的性质。

Read each section carefully before attempting the homework questions. Use the paired English and Chinese explanations to check your understanding of ionic, covalent and metallic bonding.

在开始做作业题之前，请仔细阅读每一节。利用中英对照的讲解来检查你对离子键、共价键和金属键的理解。

---

1. Core Ideas of Bonding | 键合的核心思想

Atoms bond to achieve a more stable electron arrangement. For most atoms, this means having a full outer shell, often called a noble gas configuration because the noble gases are already stable.

原子键合是为了获得更稳定的电子排布。对大多数原子来说，这意味着拥有满外层，通常称为稀有气体构型，因为稀有气体本身就是稳定的。

The number of electrons in the outer shell controls how an atom bonds. Metals tend to lose electrons to form positive ions, while non-metals tend to gain or share electrons to fill their outer shells.

外层电子数控制原子的键合方式。金属倾向于失去电子形成正离子，而非金属倾向于获得或共享电子以填满外层。

This unit uses three models to explain bonding: ionic bonding, covalent bonding and metallic bonding. Each model links a particular type of particle to a set of observable properties.

本单元使用三种模型来解释键合：离子键、共价键和金属键。每种模型都将特定类型的粒子与一组可观察的性质联系起来。

When you answer homework questions, always connect the structure to the property. For example, a high melting point tells you that strong forces must be overcome before the substance changes state.

回答作业题时，始终将结构与性质联系起来。例如，高熔点说明在物质发生状态变化之前，必须克服很强的力。

---

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

Ionic bonding happens between a metal and a non-metal. The metal atom transfers one or more electrons to the non-metal atom, so both ions achieve full outer shells.

离子键发生在金属和非金属之间。金属原子将一个或多个电子转移给非金属原子，因此两种离子都能达到满外层。

Metal atoms form positive ions called cations. Examples include Na⁺, Mg²⁺ and Al³⁺. Non-metal atoms form negative ions called anions, such as Cl⁻, O²⁻ and N³⁻.

金属原子形成正离子，称为阳离子。例如 Na⁺、Mg²⁺ 和 Al³⁺。非金属原子形成负离子，称为阴离子，例如 Cl⁻、O²⁻ 和 N³⁻。

The oppositely charged ions attract each other strongly in a giant ionic lattice. Sodium chloride can be represented as Na⁺Cl⁻, and magnesium oxide as Mg²⁺O²⁻.

带相反电荷的离子在巨型离子晶格中强烈相互吸引。氯化钠可表示为 Na⁺Cl⁻，氧化镁可表示为 Mg²⁺O²⁻。

In a dot-and-cross diagram, you must show the electron transfer clearly from the metal to the non-metal. Draw the resulting ions separately with full outer shells and correct charges.

在点叉图中，你必须清楚地画出电子从金属转移到非金属。分别画出生成的离子，外层要满，电荷要正确。

An ion is a charged particle formed when an atom loses or gains electrons. The proton number does not change, but the number of electrons becomes different from the number of protons.

离子是原子失去或得到电子后形成的带电粒子。质子数不变，但电子数与质子数不同。

---

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

Ionic compounds have high melting and boiling points because the giant ionic lattice contains strong electrostatic forces between oppositely charged ions. A large amount of energy is needed to overcome these forces.

离子化合物具有高熔点和高沸点，因为巨型离子晶格中带相反电荷的离子之间存在强静电引力。克服这些力需要大量能量。

Solid ionic compounds do not conduct electricity because the ions are fixed in the lattice and cannot move to carry charge. Ions can only conduct when they become free to move.

固态离子化合物不导电，因为离子被固定在晶格中，不能移动以携带电荷。离子只有在自由移动时才能导电。

When an ionic compound is melted or dissolved in water, the lattice breaks down and the ions become free to move. This allows the liquid or solution to conduct electricity.

当离子化合物熔融或溶于水时，晶格被破坏，离子可以自由移动。这使得液体或溶液能够导电。

Many ionic compounds are brittle. If a force shifts the layers of ions, ions with the same charge can become aligned and repel each other, causing the solid to break.

许多离子化合物很脆。如果外力使离子层错位，同种电荷的离子会相互对齐并排斥，导致固体破裂。

---

4. Covalent Bonding: Electron Sharing | 共价键：电子共享

Covalent bonding happens between non-metal atoms. Instead of transferring electrons, the atoms share pairs of electrons so that each atom can count a full outer shell.

共价键发生在非金属原子之间。原子不是转移电子，而是共享成对电子，使每个原子都可以算作拥有满外层。

A single covalent bond shares one pair of electrons, for example H₂ and Cl₂. A double bond shares two pairs, as in O₂, and a triple bond shares three pairs, as in N₂.

单共价键共享一对电子，例如 H₂ 和 Cl₂。双键共享两对电子，如 O₂，三键共享三对电子，如 N₂。

Common covalent molecules include water H₂O, carbon dioxide CO₂ and methane CH₄. The formula of a covalent molecule depends on how many electrons each atom needs to gain by sharing.

常见共价分子包括水 H₂O、二氧化碳 CO₂ 和甲烷 CH₄。共价分子的化学式取决于每个原子通过共享需要获得多少电子。

In a dot-and-cross diagram for a covalent molecule, show only the outer shell electrons. Place the shared pairs

Published by TutorHao | Exam Prep Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）