📚 Atoms, Elements, and Compounds: The Building Blocks of Matter | 原子、元素与化合物：物质的基本组成
Everything in the universe is made of matter. To understand the world of science, we first need to understand the tiny particles that form the basis of all substances. This revision guide covers the core ideas of atomic structure, elements, compounds, and chemical bonding – essential topics for Edexcel IGCSE Science.
宇宙中的一切都是由物质构成的。要理解科学世界，我们首先需要了解构成所有物质基础的微小粒子。本复习指南涵盖了原子结构、元素、化合物和化学键的核心概念，这是 Edexcel IGCSE 科学的关键主题。
1. The Particle Theory of Matter | 物质的粒子理论
The particle theory states that all matter is made up of tiny particles that are constantly moving. There are empty spaces between the particles, and the particles are attracted to each other. When a substance is heated, the particles gain energy and move faster.
粒子理论指出，所有物质都是由不断运动的微小粒子组成的。粒子之间存在空隙，且粒子之间相互吸引。当物质受热时，粒子获得能量并运动得更快。
There are three states of matter: solid, liquid, and gas. In a solid, particles are arranged in a regular pattern and vibrate around fixed positions. In a liquid, particles are close together but can move past each other. In a gas, particles are far apart and move freely at high speeds.
物质有三种状态：固态、液态和气态。在固体中，粒子呈规则排列并在固定位置附近振动；在液体中，粒子紧密相连但可以相互滑动；在气体中，粒子间距大，并高速自由运动。
- Solid – fixed shape and volume, very hard to compress.
- Liquid – fixed volume but no fixed shape, can flow.
- Gas – no fixed shape or volume, can be compressed easily.
- 固体 – 形状和体积固定，难以压缩。
- 液体 – 体积固定但形状不固定，可以流动。
- 气体 – 形状和体积都不固定，容易压缩。
2. Atomic Structure | 原子结构
An atom is the smallest particle of an element that can take part in a chemical reaction. It consists of three types of subatomic particles: protons, neutrons, and electrons.
原子是元素在化学反应中能参与变化的最小粒子。它由三种亚原子粒子组成：质子、中子和电子。
Protons have a positive charge and a relative mass of 1. Neutrons have no charge and a relative mass of 1. Electrons have a negative charge and a very small mass (about 1/1840 of a proton). Protons and neutrons are located in the dense central region called the nucleus, while electrons move around the nucleus in energy levels.
质子带正电，相对质量为 1；中子不带电，相对质量也为 1；电子带负电，质量非常小（约为质子的 1/1840）。质子和中子位于称为原子核的致密中心区域，而电子则在核外的能层中运动。
| Particle | Charge | Relative mass | Location |
| Proton | +1 | 1 | Nucleus |
| Neutron | 0 | 1 | Nucleus |
| Electron | –1 | 1/1840 | Energy levels |
| 粒子 | 电荷 | 相对质量 | 位置 |
| 质子 | +1 | 1 | 原子核 |
| 中子 | 0 | 1 | 原子核 |
| 电子 | –1 | 1/1840 | 能层 |
3. Elements, Compounds, and Mixtures | 元素、化合物与混合物
An element is a pure substance that contains only one type of atom. A compound is a pure substance made from two or more elements that are chemically combined in a fixed ratio. A mixture contains two or more substances (elements or compounds) that are physically combined and can be separated by physical methods.
元素是只含有一种原子的纯净物。化合物是由两种或多种元素以固定比例化学结合成的纯净物。混合物含有两种或多种物质（元素或化合物），它们只是物理结合，可以通过物理方法分离。
The properties of a compound are different from the properties of the elements that form it. For example, sodium is a reactive metal and chlorine is a toxic gas, but sodium chloride (table salt) is a harmless white solid. Mixtures retain the properties of the original substances.
化合物的性质与其组成元素的性质不同。例如，钠是活泼金属，氯是有毒气体，但氯化钠（食盐）是无害的白色固体。而混合物保持各组分原有的性质。
4. How to Separate Mixtures | 如何分离混合物
Different separation techniques are used depending on the physical properties of the substances in a mixture.
根据混合物中各物质物理性质的不同，可以使用不同的分离方法。
- Filtration – separates insoluble solids from liquids (e.g., sand from water).
- Evaporation – removes a solvent from a solution to obtain a soluble solid (e.g., salt from salt water).
- Distillation – separates a liquid from a solution or two liquids with different boiling points (e.g., pure water from ink).
- Chromatography – separates dissolved substances based on their different movement speeds on a medium (e.g., dyes in a pen).
- 过滤 – 分离不溶性固体与液体（如从水中分离沙）。
- 蒸发 – 通过除去溶剂来获得可溶性固体（如从盐水中得到盐）。
- 蒸馏 – 从溶液中分离液体，或分离沸点不同的两种液体（如从墨水中提纯水）。
- 色谱法 – 根据溶解物质在介质上不同的移动速度进行分离（如分离笔中的染料）。
5. Using the Periodic Table | 使用元素周期表
The periodic table arranges all known elements in order of increasing atomic number. The vertical columns are called groups, and the horizontal rows are called periods. Elements in the same group have the same number of outer electrons and thus similar chemical properties.
元素周期表将已知元素按原子序数递增排列。纵列称为族，横行称为周期。同一族的元素最外层电子数相同，因此化学性质相似。
Group 1 elements are the alkali metals, Group 2 are the alkaline earth metals, Group 7 are the halogens, and Group 8/0 are the noble gases. Metals are found on the left side of the table, while non-metals are on the right side.
第 1 族元素是碱金属，第 2 族是碱土金属，第 7 族是卤素，第 8/0 族是稀有气体。金属位于周期表左侧，非金属位于右侧。
6. Atomic Number, Mass Number, and Isotopes | 原子序数、质量数与同位素
The atomic number (Z) is the number of protons in the nucleus. In a neutral atom, the number of electrons equals the number of protons. The mass number (A) is the total number of protons and neutrons.
原子序数（Z）是原子核中的质子数。在电中性的原子中，电子数等于质子数。质量数（A）是质子数与中子数之和。
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. For example, carbon-12 and carbon-14 are both carbon isotopes; they have 6 protons but 6 and 8 neutrons, respectively.
同位素是同一元素中质子数相同但中子数不同的原子。例如，碳-12 和碳-14 都是碳的同位素；它们都有 6 个质子，但分别有 6 个和 8 个中子。
Mass number (A) = Number of protons + Number of neutrons
质量数（A）= 质子数 + 中子数
7. Electron Configuration | 电子排布
Electrons are arranged in energy levels (shells) around the nucleus. The lowest energy level is closest to the nucleus. Electrons usually fill the lowest energy levels first. The first shell can hold a maximum of 2 electrons, and the second and third shells can hold a maximum of 8 electrons each.
电子在原子核周围的能层（壳层）中排列。最低能层最靠近原子核。电子通常优先填充最低能层。第一层最多容纳 2 个电子，第二层和第三层最多各容纳 8 个电子。
For example, the electron configuration of sodium (atomic number 11) is 2, 8, 1. This configuration determines how the atom reacts with other atoms.
例如，钠（原子序数 11）的电子排布是 2, 8, 1。这种排布决定了该原子与其他原子反应的方式。
8. The Development of the Atomic Model | 原子模型的发展
The atomic model has changed over time. John Dalton proposed that atoms were solid spheres. J.J. Thomson discovered the electron and developed the “plum pudding” model, where electrons are embedded in a positive sphere. Ernest Rutherford conducted the gold foil experiment, which showed that atoms are mostly empty space with a small, dense positive nucleus. Niels Bohr then stated that electrons orbit the nucleus in specific energy levels.
原子模型随着时间的推移而不断发展。约翰·道尔顿提出原子是实心球体。J.J. 汤姆逊发现了电子并提出了“葡萄干布丁”模型，认为电子镶嵌在带正电的球体中。欧内斯特·卢瑟福通过金箔实验证明原子大部分是空的空间，并有一个微小而致密的正电核。尼尔斯·玻尔随后提出电子在特定的能层中绕核运动。
Later models introduced the idea of electron clouds and subatomic particles such as quarks, but for IGCSE, the Bohr model with energy levels is sufficient.
后来的模型引入了电子云和夸克等亚原子粒子的概念，但就 IGCSE 而言，掌握玻尔的能层模型就已足够。
9. Ionic Bonding | 离子键
Ionic bonding occurs between a metal and a non-metal. The metal atom loses one or more electrons to become a positive ion (cation), and the non-metal atom gains those electrons to become a negative ion (anion). The strong electrostatic attraction between oppositely charged ions forms the ionic bond.
离子键发生在金属与非金属之间。金属原子失去一个或多个电子形成带正电的阳离子，非金属原子获得这些电子形成带负电的阴离子。带相反电荷的离子之间强烈的静电引力形成了离子键。
For example, sodium (2, 8, 1) loses one electron to form Na⁺, and chlorine (2, 8, 7) gains one electron to form Cl⁻. The compound formed is sodium chloride (Na⁺Cl⁻), which has a giant ionic lattice structure.
例如，钠（2, 8, 1）失去一个电子形成 Na⁺，氯（2, 8, 7）得到一个电子形成 Cl⁻。生成的化合物是氯化钠（Na⁺Cl⁻），具有巨大的离子晶格结构。
10. Covalent Bonding | 共价键
Covalent bonding occurs between non-metal atoms. When two non-metal atoms share one or more pairs of electrons, a covalent bond is formed. The shared electrons are attracted to both nuclei, holding the atoms together.
共价键发生在非金属原子之间。当两个非金属原子共享一对或多对电子时，就形成了共价键。共享电子受到两个原子核的共同吸引，从而将原子结合在一起。
Examples include water, H₂O; carbon dioxide, CO₂; and methane, CH₄. Simple molecular substances have low melting and boiling points because the intermolecular forces are weak, although the covalent bonds themselves are strong.
例如：水（H₂O）、二氧化碳（CO₂）和甲烷（CH₄）。简单分子物质具有较低的熔沸点，因为分子间作用力较弱，尽管共价键本身很强。
11. Metallic Bonding | 金属键
Metallic bonding occurs in metals. Metal atoms lose their outer electrons to form positive ions, and these delocalised electrons move freely between the ions. The strong electrostatic attraction between the positive ions and the mobile electrons is called metallic bonding.
金属键发生在金属中。金属原子失去外层电子形成正离子，这些离域电子在离子之间自由移动。正离子与流动电子之间的强烈静电引力称为金属键。
This model explains why metals are good conductors of electricity and heat, are malleable and ductile, and often have high melting points. The freely moving electrons carry charge and energy through the metal.
该模型解释了金属为什么是良好的电和热导体、具有延展性和可锻性，并且通常熔点较高。自由移动的电子在金属中传递电荷和能量。
Published by TutorHao | Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导Cancel reply