Edexcel A-Level Chemistry 104: Inorganic Chemistry and the Periodic Table | 爱德思A-Level化学104：无机化学与元素周期表

📚 Edexcel A-Level Chemistry 104: Inorganic Chemistry and the Periodic Table | 爱德思A-Level化学104：无机化学与元素周期表

This Edexcel A-Level Chemistry unit, Combined 104, brings together periodicity, Group 2 and Group 7 chemistry, redox displacement reactions and qualitative analysis. Understanding these patterns is essential for both written papers and practical-based questions.

本单元为爱德思A-Level化学 Combined 104，内容包括周期性、第2族与第7族化学、氧化还原置换反应以及定性分析。掌握这些规律对笔试和实验类题目都至关重要。

1. Periodicity: Repeating Trends Across a Period | 周期性：同一周期中的递变规律

Periodicity describes the repeating pattern of physical and chemical properties across a period in the Periodic Table. Across Period 3 from sodium to argon, atomic radius generally decreases, first ionisation energy generally increases, and electronegativity increases.

周期性是指元素性质在同一周期中呈现重复递变的规律。第3周期从钠到氩，原子半径总体减小，第一电离能总体增大，电负性也增大。

The three main factors controlling periodicity are nuclear charge, electron shielding and atomic radius. An increase in nuclear charge attracts electrons more strongly, while extra inner shells increase shielding and reduce attraction.

控制周期性的三个主要因素是核电荷、电子屏蔽和原子半径。核电荷增大使电子受到更强吸引，而内层电子增加会增强屏蔽并减弱吸引。

• Across a period: nuclear charge increases, shielding stays similar, radius decreases.
• Down a group: nuclear charge increases, shielding increases, radius increases.

• 同一周期从左到右：核电荷增大，屏蔽变化不大，半径减小。
• 同一族从上到下：核电荷增大，屏蔽增加，半径增大。

2. First Ionisation Energy and Its Exceptions | 第一电离能及其例外

The first ionisation energy is the energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions. It is represented as:

第一电离能是指从一摩尔气态原子中移除一摩尔电子，形成一摩尔气态 1+ 离子所需的能量。可表示为：

X(g) → X⁺(g) + e⁻

Across a period, first ionisation energy generally increases because the nuclear charge increases while shielding stays similar. However, there are two important exceptions between Be and B, and between N and O.

同一周期中第一电离能总体增大，因为核电荷增加而屏蔽几乎不变。但在 Be 与 B、N 与 O 之间存在两个重要例外。

• Boron has a lower first ionisation energy than beryllium because the 2p electron is at a higher energy level than the 2s electron.
• Oxygen has a lower first ionisation energy than nitrogen because oxygen has a paired electron in one 2p orbital, causing electron-electron repulsion.

• 硼的第一电离能低于铍，因为 2p 电子比 2s 电子能量更高。
• 氧的第一电离能低于氮，因为氧在同一个 2p 轨道中有一对成对电子，产生电子-电子排斥。

3. Blocks of the Periodic Table | 周期表分区

The Periodic Table is divided into s-block, p-block and d-block based on the highest-energy sub-shell being filled. Group 1 and Group 2 are in the s-block, Groups 3 to 0 are in the p-block, and transition metals are in the d-block.

周期表根据最高能级亚层分为 s 区、p 区和 d 区。第1族和第2族位于 s 区，第3至 0 族位于 p 区，过渡金属位于 d 区。

In Edexcel A-Level Chemistry, understanding electron configuration helps explain why elements in the same block show similar properties. For example, Group 2 elements all have the outer electron configuration ns².

在爱德思A-Level化学中，理解电子构型有助于解释为什么同一区元素具有相似性质。例如，第2族元素外层电子构型均为 ns²。

Knowing period and group from electron configuration is a common examination skill. An element with outer configuration 3s² is in Period 3, Group 2, and is magnesium.

根据电子构型判断周期和族是常见考点。外层构型为 3s² 的元素位于第3周期、第2族，即镁。

4. Group 2: Alkaline Earth Metals | 第2族：碱土金属

Group 2 elements include beryllium, magnesium, calcium, strontium, barium and radium. Down Group 2, atomic radius increases, first ionisation energy decreases, and reactivity increases.

第2族元素包括铍、镁、钙、锶、钡和镭。沿第2族从上到下，原子半径增大，第一电离能减小，反应性增强。

The Group 2 metals form 2+ ions by losing their two outer s electrons. The general half-equation for oxidation is:

第2族金属通过失去两个外层 s 电子形成 2+ 离子。氧化的一般半反应式为：

M(g) → M²⁺(g) + 2e⁻

Because ionisation energy decreases down the group, barium reacts more vigorously with water than calcium. This trend is important when comparing the reactions of magnesium and calcium with dilute acid.

由于电离能沿族递减，钡与水的反应比钙更剧烈。

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