📚 Appendix 1: The Periodic Table of the Elements | 附录1：元素周期表
The Periodic Table of the Elements in Appendix 1 of the Cambridge International AS and A Level Chemistry Data Booklet is not just a reference list; it is a condensed map of atomic structure and chemical behaviour. Students are expected to use it quickly and accurately to extract relative atomic masses, atomic numbers, symbols, and names, and to link position to trends and bonding.
剑桥国际 AS 与 A Level 化学数据手册附录 1 中的元素周期表不仅是一份参考清单，更是一张浓缩的原子结构与化学行为地图。考生需要快速、准确地从中提取相对原子质量、原子序数、元素符号和名称，并将元素位置与周期性趋势和成键方式联系起来。
1. Purpose and Layout | 用途与布局
The Cambridge periodic table is arranged by increasing atomic number. Each cell normally shows the element symbol, atomic number, and relative atomic mass. It is divided into periods (horizontal rows) and groups (vertical columns). The full IUPAC version numbers groups 1-18, but some exam questions still use older labels such as Group I, Group II, Group VII, and Group 0.
剑桥周期表按原子序数递增排列。每个元素格通常显示元素符号、原子序数和相对原子质量。表格分为周期（横行）和族（纵列）。完整 IUPAC 版本将族编号为 1-18，但部分试题仍使用旧标签，如第 I 族、第 II 族、第 VII 族和第 0 族。
The older group labels can be mapped to the modern IUPAC numbers: Group I = Group 1, Group II = Group 2, Group VII = Group 17, and Group 0 = Group 18. Transition metals occupy the central d-block and are often labelled Groups 3-12.
旧族标签可以对应到现代 IUPAC 编号：第 I 族 = 第 1 族，第 II 族 = 第 2 族，第 VII 族 = 第 17 族，第 0 族 = 第 18 族。过渡金属占据中间的 d 区，通常标记为第 3-12 族。
2. Reading the Data Booklet Table | 如何阅读数据手册中的周期表
When using Appendix 1, always check which number is the atomic number and which is the relative atomic mass. The smaller whole number is the atomic number, and the larger decimal value is the relative atomic mass. For example, chlorine has atomic number 17 and relative atomic mass 35.5. This distinction matters when calculating molar masses and identifying isotopes.
使用附录 1 时，务必分清哪个数字是原子序数，哪个是相对原子质量。较小的整数是原子序数，较大的小数值是相对原子质量。例如，氯的原子序数为 17，相对原子质量为 35.5。在计算摩尔质量和识别同位素时，这一区分非常重要。
Relative atomic masses in the data booklet are given to one decimal place for most elements, such as carbon 12.0, oxygen 16.0, and iron 55.8. In calculations, always use the value exactly as printed in the booklet unless the question specifies otherwise.
数据手册中大多数元素的相对原子质量保留一位小数，例如碳 12.0、氧 16.0、铁 55.8。在计算中，除非题目另有说明，否则应严格使用手册中印出的数值。
3. Periods, Groups and Blocks | 周期、族与电子区
The table can be divided into s-block, p-block, d-block, and f-block elements. s-block contains Groups 1 and 2; p-block contains Groups 13 to 18; d-block contains the transition metals in Groups 3 to 12. The block is determined by the highest-energy sub-shell being filled. For A Level, questions usually focus on s-, p-, and d-block elements.
周期表可分为 s 区、p 区、d 区和 f 区元素。s 区包含第 1 和第 2 族；p 区包含第 13 至第 18 族；d 区包含第 3 至第 12 族的过渡金属。区由最高能量的电子亚层决定。A Level 考试通常聚焦于 s 区、p 区和 d 区元素。
The period number tells you the highest occupied principal quantum shell. For example, elements in Period 2 all have their outermost electrons in the second shell, while elements in Period 4 have electrons entering the fourth shell. This helps explain why atomic and ionic radii change systematically.
周期数表示最高占据的主量子壳层。例如，第 2 周期元素的最外层电子都在第二壳层，而第 4 周期元素的电子进入第四壳层。这有助于解释原子半径和离子半径为何呈系统性变化。
4. Electronic Configurations and Position | 电子构型与元素位置
The position of an element indicates its outer electron configuration. Group number for s-block and p-block elements gives the number of outer-shell electrons, while period number gives the highest occupied principal quantum shell. For example, phosphorus in Period 3, Group 15 has configuration 1s² 2s² 2p⁶ 3s² 3p³. This link is essential for explaining trends and ion formation.
元素的位置可以揭示其外层电子构型。s 区和 p 区元素的族数等于最外层电子数，周期数等于最高占据主量子壳层。例如，磷位于第 3 周期、第 15 族，其电子构型为 1s² 2s² 2p⁶ 3s² 3p³。这一联系对于解释趋势和离子形成至关重要。
Transition metals have more complex electronic configurations because the 3d and 4s sub-shells are close in energy. For example, chromium and copper show special configurations: Cr is [Ar] 3d⁵ 4s¹ and Cu is [Ar] 3d¹⁰ 4s¹. These exceptions arise from the extra stability of half-filled and fully filled d sub-shells.
过渡金属的电子构型较为复杂，因为 3d 和 4s 亚层能量相近。例如，铬和铜表现出特殊构型：Cr 为 [Ar] 3d⁵ 4s¹，Cu 为 [Ar] 3d¹⁰ 4s¹。这些例外源于半充满和全充满 d 亚层具有额外稳定性。
5. Atomic Radius Trend | 原子半径趋势
Atomic radius decreases across a period because the nuclear charge increases while shielding from inner shells remains approximately constant. The greater effective nuclear charge pulls the outer electrons closer. Down a group, atomic radius increases because additional electron shells are added and shielding increases, so outer electrons are held less tightly.
原子半径在同一周期从左到右减小，因为核电荷增加，而内层电子的屏蔽作用大致不变。有效核电荷增大，使外层电子被拉得更近。沿着族从上到下，原子半径增大，因为增加了新的电子壳层，屏蔽增强，外层电子被束缚得较松。
For example, across Period 3 from sodium to chlorine, atomic radius decreases steadily from 186 pm to 99 pm. Down Group 1, atomic radius increases from lithium 152 pm to caesium 262 pm. These values are useful for comparing bonding strength and reactivity.
例如，在第 3 周期中从钠到氯，原子半径从 186 pm 稳定减小至 99 pm。沿第 1 族从上到下，原子半径从锂的 152 pm 增大至铯的 262 pm。这些数值有助于比较键合强度和反应活性。
6. Ionic Radius Trend | 离子半径趋势
Positive ions are smaller than their parent atoms because the loss of outer electrons reduces electron-electron repulsion and often removes the outermost shell. Negative ions are larger than their parent atoms because added electrons increase repulsion. For isoelectronic ions, radius decreases as nuclear charge increases. For example, N³⁻ > O²⁻ > F⁻ > Na⁺ > Mg²⁺ > Al³⁺.
阳离子比其母原子小，因为失去外层电子后电子间斥力减小，并且常常移除了最外电子层。阴离子比其母原子大，因为增加的电子使排斥作用增强。对于等电子离子，半径随核电荷增加而减小。例如：N³⁻ > O²⁻ > F⁻ > Na⁺ > Mg²⁺ > Al³⁺。
The same trend is seen in isoelectronic species with 18 electrons: P³⁻ > S²⁻ > Cl⁻ > K⁺ > Ca²⁺. When comparing ions, always identify the electron configuration first, then use nuclear charge to explain the size order.
同样的趋势也出现在具有 18 个电子的等电子物种中：P³⁻ > S²⁻ > Cl⁻ > K⁺ > Ca²⁺。比较离子时，应首先确定电子构型，再利用核电荷解释大小顺序。
7. First Ionisation Energy | 第一电离能
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 singly charged positive ions. It generally increases across a period and decreases down a group. However, there are two important dips: between Group 2 and Group 13, and between Group 15 and Group 16.
第一电离能是指从一摩尔气态原子中移走一摩尔电子，形成一摩尔气态正一价离子所需的能量。它通常在同一周期从左到右增大，沿族从上到下减小。但有两处重要下降：第 2 族与第 13 族之间，以及第 15 族与第 16 族之间。
Li(g) → Li⁺(g) + e⁻
For example, the first ionisation energy of lithium can be represented by Li(g) → Li⁺(g) + e⁻, where all species are in the gaseous state. Standard enthalpy conditions are often assumed, and values are quoted in kJ mol⁻¹.
例如，锂的第一电离能可表示为 Li(g) → Li⁺(g) + e⁻，其中所有物种均为气态。通常采用标准焓条件，数值以 kJ mol⁻¹ 为单位。
The dip from Group 2 to Group 13 occurs because the outermost electron in Group 13 enters a p sub-shell of slightly higher energy than the s sub-shell. The dip from Group 15 to Group 16 occurs because the p sub-shell in Group 16 gains a paired electron, causing increased electron-electron repulsion and making removal easier.
第 2 族到第 13 族的下降是因为第 13 族最外层电子进入能量略高于 s 亚层的 p 亚层。第 15 族到第 16 族的下降是因为第 16 族的 p 亚层出现电子配对，电子间斥力增大，使电子更容易被移走。
8. Electronegativity | 电负性
Electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond. On the Pauling scale, fluorine is the most electronegative element with a value of 4.0. Electronegativity increases across a period and decreases down a group. Noble gases are often excluded because they usually do not form covalent bonds.
电负性是指原子在共价键中吸引成键电子的能力。在鲍林标度中，氟是电负性最大的元素，数值为 4.0。电负性在同一周期从左到右增大，沿族从上到下减小。稀有气体通常不参与比较，因为它们一般不易形成共价键。
Large electronegativity differences lead to ionic bonding, while small differences lead to covalent bonding. For example, sodium (0.9) and chlorine (3.0) have a difference of 2.1, so NaCl is ionic. Carbon (2.5) and hydrogen (2.1) have a difference of only 0.4, so C-H bonds are covalent.
电负性差异大时形成离子键，差异小时形成共价键。例如，钠（0.9）与氯（3.0）的差值为 2.1，因此 NaCl 为离子化合物。碳（2.5）与氢（2.1）的差值仅为 0.4，因此 C-H 键为共价键。
9. Melting and Boiling Points Across Periods | 周期内熔沸点变化
Melting and boiling points show a characteristic pattern across Period 3. Sodium, magnesium, and aluminium are metals with increasing melting points due to stronger metallic bonding from higher charge density. Silicon has the highest melting point because of its giant covalent structure. Phosphorus, sulfur, chlorine, and argon are simple molecular with low melting and boiling points.
第 3 周期元素的熔点和沸点呈现典型规律。钠、镁、铝为金属，随着电荷密度增大，金属键增强，熔点依次升高。硅因具有巨型共价结构而熔点最高。磷、硫、氯和氩为简单分子，熔点和沸点较低。
- Na < Mg < Al: metallic bonding strength increases | 金属键增强
- Si: giant covalent, highest melting point in Period 3 | 巨型共价，第 3 周期熔点最高
- P₄, S₈, Cl₂, Ar: weak van der Waals forces | 弱范德华力
In Period 2, carbon as diamond or graphite has a very high melting point due to giant covalent bonding, while nitrogen
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