Year 7 CAIE Chemistry: Formula and Theorem Quick Reference Handbook | Year 7 CAIE 化学：公式定理速查手册

📚 Year 7 CAIE Chemistry: Formula and Theorem Quick Reference Handbook | Year 7 CAIE 化学：公式定理速查手册

This quick reference handbook gathers the essential formulas, rules, and key concepts for Year 7 CAIE Chemistry. It is designed to help you revise atomic structure, formula writing, balancing equations, and more. Keep it handy whenever you need to check a definition or apply a rule.

这本速查手册汇总了 Year 7 CAIE 化学的核心公式、定理与关键概念。无论是原子结构、化学式书写还是方程式配平，你都能在这里快速找到定义和步骤。建议在复习时随时查阅，把它们牢牢掌握。

1. States of Matter and Changes | 物质状态与变化

All matter exists in one of three common states: solid, liquid, or gas. The particles in a solid are tightly packed in a fixed arrangement, so solids have a definite shape and volume.

所有物质都以固态、液态或气态三种常见状态之一存在。固体中的粒子紧密排列在固定位置上，因此固体有确定的形状和体积。

In a liquid, particles are still close together but can move past each other. Liquids have a fixed volume but take the shape of their container.

液体中的粒子仍然彼此靠近，但可以相对滑动。液体具有固定的体积，但形状随容器而变。

In a gas, particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume and can be compressed easily.

气体中的粒子相距很远，快速地向各个方向运动。气体没有固定的形状和体积，容易被压缩。

The changes between states have specific names: melting (solid to liquid), freezing (liquid to solid), evaporation/boiling (liquid to gas), condensation (gas to liquid), sublimation (solid to gas) and deposition (gas to solid).

状态之间的变化有专门的名称：熔化（固态 → 液态）、凝固（液态 → 固态）、蒸发/沸腾（液态 → 气态）、冷凝（气态 → 液态）、升华（固态 → 气态）和凝华（气态 → 固态）。

When writing chemical equations, we often indicate the state of each substance using state symbols: (s) for solid, (l) for liquid, (g) for gas, and (aq) for an aqueous solution dissolved in water.

书写化学方程式时，我们常用状态符号标明物质的状态：(s) 表示固体，(l) 表示液体，(g) 表示气体，(aq) 表示水溶液。

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2. Atomic Structure | 原子结构

An atom is the smallest particle of an element that still shows its chemical properties. It consists of three types of subatomic particles: protons, neutrons, and electrons.

原子是元素的最小粒子，仍保持该元素的化学性质。原子由三种亚原子粒子组成：质子、中子和电子。

Protons are positively charged and found in the nucleus. Neutrons have no charge and are also in the nucleus. Electrons are negatively charged and orbit the nucleus in shells.

质子带正电，位于原子核中。中子不带电，也位于原子核中。电子带负电，在核外的电子层上运动。

The atomic number (Z) of an element is the number of protons in the nucleus. In a neutral atom, the number of electrons equals the number of protons.

元素的原子序数 (Z) 是原子核中的质子数。在中性原子中，电子数等于质子数。

Atomic Number (Z) = number of protons = number of electrons (in a neutral atom)

原子序数 (Z) = 质子数 = 电子数（中性原子）

The mass number (A) is the total number of protons and neutrons in the nucleus. The number of neutrons can be found by subtracting the atomic number from the mass number.

质量数 (A) 是原子核中质子数与中子数的总和。中子数可以通过质量数减去原子序数来计算。

Mass Number (A) = number of protons + number of neutrons

质量数 (A) = 质子数 + 中子数

Number of neutrons = A – Z

中子数 = A – Z

Electrons are arranged in shells around the nucleus. The first shell holds up to 2 electrons, the second up to 8, and the third up to 8 for the first 20 elements.

电子在原子核外的电子层上排布。第一层最多容纳 2 个电子，第二层最多 8 个，对于前 20 号元素第三层也最多 8 个。

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3. Elements, Compounds, and Mixtures | 元素、化合物与混合物

An element is a pure substance made of only one type of atom. It cannot be broken down into simpler substances by chemical means.

元素是只由一种原子组成的纯物质。它不能通过化学方法分解成更简单的物质。

A compound is a pure substance made of two or more different types of atoms chemically bonded together. It has a fixed composition and can be separated only by chemical reactions.

化合物是由两种或多种不同原子通过化学键结合形成的纯物质。它具有固定的组成，只能通过化学反应才能分离。

A mixture consists of two or more substances (elements or compounds) that are physically mixed together, not chemically combined. Each substance keeps its own properties and mixtures can be separated by physical methods.

混合物是由两种或多种物质（元素或化合物）物理混合而成的，它们之间没有发生化学结合。每种物质保持其自身的性质，混合物可以用物理方法分离。

When atoms join together they form molecules. A molecule can be an element (e.g., O₂) or a compound (e.g., H₂O).

原子结合在一起形成分子。分子可以是单质（如 O₂），也可以是化合物（如 H₂O）。

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4. The Periodic Table Basics | 元素周期表基础

The periodic table arranges all known elements in order of increasing atomic number. The horizontal rows are called periods, and the vertical columns are called groups.

元素周期表将所有已知元素按原子序数递增的顺序排列。水平的行称为周期，竖直的列称为族。

Elements in the same group have the same number of electrons in their outer shell and therefore show similar chemical properties.

同一族中的元素具有相同的最外层电子数，因此表现出相似的化学性质。

Metals are found on the left side of the periodic table; non-metals are on the right. A zig-zag line separates them.

金属位于周期表的左侧，非金属位于右侧，中间有一条锯齿形的分界线。

Here are the first 20 elements with their symbols and names:

以下是前 20 号元素的符号与中英文名称：

Atomic Number 原子序数	Symbol 符号	English Name	中文名称
1	H	Hydrogen	氢
2	He	Helium	氦
3	Li	Lithium	锂
4	Be	Beryllium	铍
5	B	Boron	硼
6	C	Carbon	碳
7	N	Nitrogen	氮
8	O	Oxygen	氧
9	F	Fluorine	氟
10	Ne	Neon	氖
11	Na	Sodium	钠
12	Mg	Magnesium	镁
13	Al	Aluminium	铝
14	Si	Silicon	硅
15	P	Phosphorus	磷
16	S	Sulfur	硫
17	Cl	Chlorine	氯
18	Ar	Argon	氩
19	K	Potassium	钾
20	Ca	Calcium	钙

You are expected to recall the names and symbols of these elements, as they form the building blocks of all chemical formulas.

你需要记住这些元素的名称和符号，它们是所有化学式的基础。

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5. Valency and Ion Charges | 化合价与离子电荷

Valency is the combining power of an element – it tells you how many chemical bonds an atom of that element can form with other atoms.

化合价是元素的结合能力——它表示该元素的一个原子能与其他原子形成多少个化学键。

Metals tend to lose electrons to form positive ions (cations). Non-metals tend to gain electrons to form negative ions (anions). The numerical value of the ion charge is often the same as the valency.

金属倾向于失去电子形成阳离子（正离子）。非金属倾向于得到电子形成阴离子（负离子）。离子电荷的数值通常等于其化合价。

Here is a list of common valencies and ions you will use in Year 7:

以下是 Year 7 常用的化合价与离子表：

Element 元素	Symbol 符号	Common Valency 常见化合价	Ion Formed 形成离子
Hydrogen 氢	H	1	H⁺
Lithium 锂	Li	1	Li⁺
Sodium 钠	Na	1	Na⁺
Potassium 钾	K	1	K⁺
Magnesium 镁	Mg	2	Mg²⁺
Calcium 钙	Ca	2	Ca²⁺
Aluminium 铝	Al	3	Al³⁺
Oxygen 氧	O	2	O²⁻
Chlorine 氯	Cl	1	Cl⁻
Sulfur (as oxide) 硫(氧化物中)	S	2	S²⁻

There are also common groups of atoms, called polyatomic ions, that carry an overall charge: hydroxide OH⁻, sulfate SO₄²⁻, nitrate NO₃⁻, carbonate CO₃²⁻, and ammonium NH₄⁺.

还有一些常见的原子团，称为多原子离子，它们带有整体电荷：氢氧根 OH⁻、硫酸根 SO₄²⁻、硝酸根 NO₃⁻、碳酸根 CO₃²⁻ 和铵根 NH₄⁺。

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6. Writing Chemical Formulae | 书写化学式

To write the chemical formula of a compound, you need to know the symbols and valencies

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