📚 Appendix 3 The Periodic Table | 附录3 元素周期表
The periodic table is the single most important organising tool in chemistry. In CIE A-Level Chemistry, the data booklet includes Appendix 3: The Periodic Table, which lists all known elements in order of increasing atomic number. This appendix provides atomic numbers, element symbols, names and relative atomic masses, and it is used throughout Papers 1, 2 and 4. A strong understanding of how to read and apply the periodic table will help you answer questions on periodicity, bonding, inorganic chemistry and even physical calculations.
元素周期表是化学中最核心的组织工具。在 CIE A-Level 化学考试中，数据手册包含附录3：元素周期表，它按原子序数递增的顺序列出所有已知元素。该附录提供原子序数、元素符号、名称和相对原子质量，并在 Paper 1、Paper 2 和 Paper 4 中广泛使用。扎实掌握如何阅读和应用周期表将帮助你解答周期性、化学键、无机化学甚至物理计算相关的题目。
1. What Is Appendix 3? | 什么是附录3？
Appendix 3 in the CIE A-Level Chemistry data booklet is the official periodic table used in examinations. It is not simply a decorative chart; every candidate is expected to extract data quickly and accurately. The table arranges elements by atomic number and groups them according to electron configuration, which allows chemists to predict physical and chemical properties.
CIE A-Level 化学数据手册中的附录3是考试中使用的官方元素周期表。它不只是装饰性图表；每位考生都需要快速且准确地从中提取数据。该表按原子序数排列元素，并根据电子排布进行分组，这使化学家能够预测元素的物理和化学性质。
- Atomic number (Z): the number of protons in the nucleus of an atom. | 原子序数（Z）：原子核中的质子数。
- Element symbol: a one- or two-letter abbreviation used worldwide. | 元素符号：国际上通用的一或两个字母的缩写。
- Relative atomic mass (A_r): the weighted average mass of an element’s isotopes relative to 1/12 of carbon-12. | 相对原子质量（A_r）：元素同位素质量的加权平均值，相对于碳-12 的 1/12。
- Period and group position: the horizontal row and vertical column that determine chemical behaviour. | 周期和族位置：决定化学行为的横行和纵列。
2. Layout of the Periodic Table | 周期表的结构布局
The periodic table is arranged into horizontal rows called periods and vertical columns called groups. Periods are numbered 1 to 7, while groups are numbered 1 to 18 in the modern IUPAC system. Elements in the same group have the same number of outer-shell electrons, which explains their similar chemical properties.
周期表按水平行（周期）和垂直列（族）排列。周期编号为 1 至 7，族在现代 IUPAC 体系中编号为 1 至 18。同一族的元素具有相同的外层电子数，这解释了它们化学性质的相似性。
Within each period, the atomic number increases by one from left to right. The electron configuration of an element determines its position in the table. For example, sodium has the configuration 1s² 2s² 2p⁶ 3s¹ and is placed in Group 1, Period 3 because its outermost electron is in a 3s orbital.
在每一周期中，原子序数从左到右依次增加一个。元素的电子排布决定了它在表中的位置。例如，钠的电子排布为 1s² 2s² 2p⁶ 3s¹，位于第 3 周期第 1 族，因为它的最外层电子处于 3s 轨道。
| Feature | Meaning | 中文含义 |
|---|---|---|
| Period | Horizontal row; indicates the highest occupied energy level. | 横行；表示已占据的最高能级。 |
| Group | Vertical column; indicates the number of outer-shell electrons. | 纵列；表示外层电子数。 |
| Block | Region labelled s, p, d or f according to the subshell being filled. | 根据正在填充的亚层标记为 s、p、d 或 f 的区域。 |
3. Atomic Number and Relative Atomic Mass | 原子序数与相对原子质量
Every element in Appendix 3 is shown with its atomic number above the symbol and its relative atomic mass below the symbol. The atomic number defines the element: all atoms of the same element have the same number of protons. The relative atomic mass, however, is an average value that depends on the natural abundance of isotopes.
附录3 中的每个元素都在符号上方标注原子序数，在符号下方标注相对原子质量。原子序数定义了元素：同一元素的所有原子具有相同的质子数。然而，相对原子质量是一个平均值，取决于天然存在的同位素丰度。
For calculation purposes in CIE A-Level Chemistry, the relative atomic mass is given to one decimal place or as a whole number in the periodic table. Students often confuse relative atomic mass with mass number; the mass number is always an integer for a specific isotope, while relative atomic mass can be a decimal.
在 CIE A-Level 化学计算中，周期表中给出的相对原子质量通常保留一位小数或是整数。学生经常将相对原子质量与质量数混淆；对于某一特定同位素，质量数总是整数，而相对原子质量可能是小数。
A_r = Σ (isotopic mass × percentage abundance) ÷ 100
4. Metals, Non-metals and Metalloids | 金属、非金属与类金属
The periodic table can be divided broadly into metals, non-metals and metalloids. Metals occupy the left and centre of the table, including Groups 1, 2, the transition metals and the lanthanides and actinides. Non-metals are found on the upper right, while metalloids form a diagonal staircase between them.
周期表可大致分为金属、非金属和类金属。金属占据周期表的左侧和中部，包括第 1 族、第 2 族、过渡金属以及镧系和锕系元素。非金属位于右上方，类金属则在两者之间形成一条斜线阶梯。
Metals tend to lose electrons to form positive ions, conduct electricity and heat, and are malleable and ductile. Non-metals tend to gain or share electrons, are poor conductors, and are often brittle in the solid state. Metalloids such as silicon and germanium show intermediate behaviour, which makes them useful as semiconductors.
金属倾向于失去电子形成正离子，能导电导热，具有延展性和可锻性。非金属倾向于获得或共用电子，导电性差，固态时通常较脆。硅和锗等类金属表现出中间性质，因此可用作半导体材料。
5. Group Names and Key Families | 族名与关键族
Several groups in the periodic table have specific names. Group 1 elements are the alkali metals, Group 2 are the alkaline earth metals, Group 17 are the halogens, and Group 18 are the noble gases. The d-block elements between Groups 2 and 13 are known as the transition metals.
周期表中有几个族有特定名称。第 1 族元素是碱金属，第 2 族是碱土金属，第 17 族是卤素，第 18 族是稀有气体。第 2 族和第 13 族之间的 d 区元素称为过渡金属。
| Group | Name | 中文名称 |
|---|---|---|
| 1 | Alkali metals | 碱金属 |
| 2 | Alkaline earth metals | 碱土金属 |
| 17 | Halogens | 卤素 |
| 18 | Noble gases | 稀有气体 |
| 3-12 | Transition metals | 过渡金属 |
Knowing these names is essential for CIE exam questions. For example, a question may ask you to explain why alkali metals become more reactive down the group, or why noble gases are unreactive; both explanations depend on electron arrangement and atomic radius.
掌握这些名称对 CIE 考试至关重要。例如，题目可能要求你解释为什么碱金属越往下越活泼，或者为什么稀有气体不活泼；这两种解释都依赖于电子排布和原子半径。
6. Periodic Trends: Atomic Radius | 周期性趋势：原子半径
Atomic radius is the distance from the nucleus to the outermost stable electron orbital. Across a period from left to right, atomic radius generally decreases because the nuclear charge increases while the shielding effect remains approximately constant, pulling the outer electrons closer to the nucleus.
原子半径是从原子核到最外层稳定电子轨道的距离。在同周期从左到右，原子半径通常逐渐减小，因为核电荷增加而屏蔽效应基本保持不变，从而将外层电子拉得更靠近原子核。
Down a group, atomic radius increases because new electron shells are added. Each additional shell is further from the nucleus, and the increased shielding effect reduces the effective nuclear charge felt by the outer electrons.
在同族从上到下，原子半径增大，因为增加了新的电子层。每一新增的电子层离核更远，增强的屏蔽效应降低了外层电子感受到的有效核电荷。
Appendix 3 helps you visualise this trend: moving from sodium to chlorine across Period 3, the atoms become smaller despite higher atomic numbers. Moving from lithium to caesium down Group 1, the atoms become larger.
附录3 有助于你直观理解这一趋势：在第 3 周期从钠到氯，虽然原子序数增大，但原子越来越小；在第 1 族从锂到铯，原子越来越大。
7. Periodic Trends: Ionisation Energy | 周期性趋势：电离能
First ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions. The equation is:
第一电离能是指从一摩尔气态原子中移走一摩尔电子形成一摩尔气态 1+ 离子所需的能量。方程式为：
X(g) → X⁺(g) + e⁻
Across a period, ionisation energy generally increases because atomic radius decreases and nuclear charge increases, so the outer electron is held more tightly. Down a group, ionisation energy decreases because the outer electron is further from the nucleus and is more shielded, making it easier to remove.
在同周期从左到右，电离能通常逐渐增大，因为原子半径减小、核电荷增加，外层电子被束缚得更紧。在同族从上到下，电离能减小，因为外层电子离核更远且屏蔽更强，更容易被移走。
There are two important exceptions in Period 2 and 3: the drop from Group 2 to Group 13 is due to the start of a new p subshell, and the drop from Group 15 to Group 16 is due to electron-electron repulsion in a doubly occupied p orbital. CIE often tests these anomalies.
第 2 和第 3 周期有两个重要例外：从第 2 族到第 13 族电离能下降是因为开始填充新的 p 亚层；从第 15 族到第 16 族下降是因为 p 轨道中成对电子间的排斥作用。CIE 经常考查这些反常现象。
8. Periodic Trends: Electronegativity | 周期性趋势：电负性
Electronegativity is the ability of an atom in a covalent bond to attract the bonding pair of electrons. It follows a similar pattern to ionisation energy: it increases across a period and decreases down a group. Fluorine is the most electronegative element, with an assigned value of approximately 4.0 on the Pauling scale.
电负性是指共价键中原子吸引成键电子对的能力。它的变化规律与电离能相似：同周期从左到右增大，同族从上到下减小。氟是电负性最大的元素，在鲍林标度上约为 4.0。
Noble gases are usually assigned no electronegativity value because they do not readily form covalent bonds. Differences in electronegativity between two bonded atoms determine whether the bond is non-polar covalent, polar covalent or ionic.
稀有气体通常没有电负性值，因为它们不易形成共价键。两个成键原子之间的电负性差异决定了化学键是非极性共价键、极性共价键还是离子键。
For example, in the CIE syllabus, you may be asked to explain why HCl is polar while Cl₂ is non-polar. The answer depends on the electronegativity difference between hydrogen and chlorine.
例如，在 CIE 大纲中，可能要求你解释为什么 HCl 是极性分子而 Cl₂ 是非极性分子。答案取决于氢和氯之间的电负性差异。
9. Blocks and Electronic Configuration | 区与电子排布
The periodic table is divided into s, p, d and f blocks according to the subshell in which the highest-energy electrons are found. Groups 1 and 2 form the s-block; Groups 13 to 18 form the p-block; the transition metals form the d-block; and the lanthanides and actinides form the f-block.
周期表根据最高能量电子所在的亚层分为 s 区、p 区、d 区和 f 区。第 1 和第 2 族构成 s 区；第 13 至 18 族构成 p 区；过渡金属构成 d 区；镧系和锕系构成 f 区。
For example, magnesium is in the s-block because its outermost electron occupies a 3s orbital: Mg is 1s² 2s² 2p⁶ 3s². Chlorine is in the p-block because its outermost electrons occupy 3p orbitals: Cl is 1s² 2s² 2p⁶ 3s² 3p⁵. Iron is in the d-block: Fe is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s².
例如，镁位于 s 区，因为其最外层电子占据 3s 轨道：Mg 为 1s² 2s² 2p⁶ 3s²。氯位于 p 区，因为其最外层电子占据 3p 轨道：Cl 为 1s² 2s² 2p⁶ 3s² 3p⁵。铁位于 d 区：Fe 为 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²。
Understanding blocks helps you predict the type of ion an element will form. s-block metals lose electrons to achieve a noble gas configuration; p-block non-metals gain or share electrons; d-block transition metals often form several stable ions with different charges.
理解区块有助于预测元素将形成的离子类型。s 区金属失去电子以达到稀有气体电子排布；p 区非金属获得或共用电子；d 区过渡金属通常形成多种不同电荷的稳定离子。
10. Using Appendix 3 in CIE Exams | 如何在 CIE 考试中使用附录3
In a CIE A-Level Chemistry exam, you should use Appendix 3 as a quick reference tool, not as a replacement for understanding trends. For a given element, first locate it in the table, note its atomic number, group and period, then apply your knowledge of periodic trends to predict its properties.
在 CIE A-Level 化学考试中，你应将附录3 作为快速参考工具，而不是替代对趋势的理解。对于给定元素，先在表中找到它，记录其原子序数、族和周期，然后
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