📚 Sodium and Its Compounds: Essential Chemical Equations | 钠及其化合物核心方程式
Sodium (Na) is a soft, silvery alkali metal in Group 1 of the periodic table. Because it easily loses its single outer electron, it forms sodium ions, Na⁺, and a wide range of ionic compounds. In chemistry examinations, many questions focus on writing balanced equations for the reactions of sodium, sodium oxide, sodium peroxide, sodium hydroxide, sodium carbonate, and sodium hydrogencarbonate. Mastering these equations is essential for answering questions about reactions, salt preparation, and gas tests.
钠（Na）是元素周期表第ⅠA族中一种质软、呈银白色的碱金属。由于它极易失去其唯一的最外层电子，因此常形成钠离子 Na⁺，并生成种类繁多的离子化合物。在化学考试中，许多题目都会考查钠、氧化钠、过氧化钠、氢氧化钠、碳酸钠和碳酸氢钠等物质反应的配平方程式。掌握这些核心方程式，是作答有关反应、制盐和气体检验问题的关键。
1. Electron Configuration and Ionisation | 电子排布与电离
Sodium has the electronic configuration 1s² 2s² 2p⁶ 3s¹. The single 3s electron is held weakly, so sodium readily loses one electron to form a stable Na⁺ ion with a noble-gas configuration.
钠的电子排布为 1s² 2s² 2p⁶ 3s¹。最外层3s轨道上的单电子受核吸引较弱，因此钠很容易失去1个电子，形成具有稀有气体稳定结构的 Na⁺ 离子。
Na(g) → Na⁺(g) + e⁻
This electron-loss process is the first ionisation energy of sodium, and it explains why sodium behaves as such a powerful reducing agent.
上述失电子过程对应于钠的第一电离能，也解释了钠为何是强还原剂。
2. Reaction with Water | 钠与水的反应
When a small piece of sodium is added to water, it floats, melts into a silver ball, moves rapidly on the surface, and produces a colourless gas. A common exam equation is the formation of sodium hydroxide and hydrogen gas.
将一小块钠放入水中时，钠会浮在水面、熔化成银白色小球并迅速游动，同时产生无色气体。生成氢氧化钠和氢气的方程式是考试中的常见考点。
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)↑
The ionic equation better shows the electron transfer from sodium atoms to water molecules.
离子方程式可以更清楚地展示钠原子向水分子转移电子的过程。
2Na(s) + 2H₂O(l) → 2Na⁺(aq) + 2OH⁻(aq) + H₂(g)↑
The gas produced is hydrogen, which gives a characteristic “pop” with a lighted splint.
生成的氢气用燃着的木条检验时，会发出尖锐的爆鸣声。
3. Reaction with Oxygen | 钠与氧气的反应
At room temperature, sodium reacts slowly with oxygen in the air, forming sodium oxide. On heating in excess oxygen, sodium burns brightly to form sodium peroxide.
常温下，钠会缓慢与空气中的氧气反应生成氧化钠；在过量氧气中加热时，钠会剧烈燃烧并生成过氧化钠。
4Na(s) + O₂(g) → 2Na₂O(s)
2Na(s) + O₂(g) → Na₂O₂(s)
Sodium oxide itself can be oxidised further to sodium peroxide when heated in oxygen.
氧化钠在氧气中继续加热时，可进一步被氧化生成过氧化钠。
2Na₂O(s) + O₂(g) → 2Na₂O₂(s)
4. Reaction with Non-Metals | 钠与非金属的反应
Sodium reacts directly with chlorine to produce sodium chloride; the reaction is vigorous and highly exothermic.
钠能与氯气直接化合生成氯化钠，该反应剧烈且放出大量热。
2Na(s) + Cl₂(g) → 2NaCl(s)
Sodium also reacts with sulfur when warmed, producing sodium sulfide.
加热时，钠也可以与硫反应生成硫化钠。
2Na(s) + S(s) → Na₂S(s)
5. Reaction with Dilute Acids | 钠与稀酸的反应
As a very reactive metal, sodium reacts violently with dilute acids, replacing hydrogen in the acid to form a salt.
作为一种活泼金属，钠能与稀酸剧烈反应，置换出酸中的氢并生成盐。
2Na(s) + 2HCl(aq) → 2NaCl(aq) + H₂(g)↑
2Na(s)
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