氧化还原反应及第1/2族趋势
引入| English | 释义 | 拼音 |
|---|---|---|
| oxidising agent/ˈɒksɪdaɪzɪŋ ˈeɪdʒənt/ | 氧化剂 | yǎng huà jì |
| oxidation number/ˌɒksɪˈdeɪʃn ˈnʌmbə/ | 氧化数 | yǎng huà shù |
| peroxides | 过氧化物 | guò yǎng huà wù |
| shielding/ˈʃiːldɪŋ/ | 屏蔽 | píng bì |
Why is the oxidising agent 氧化剂 reduced?
- Magnesium reacting with chlorine loses electrons, while chlorine gains them. The words agent and process describe different sides of the same transfer.
- Track electron loss and gain before naming the agents.
Use oxidation-number 氧化数 bookkeeping
- Oxidation-number values add to the species charge. Elements are zero; oxygen is usually −2 but −1 in peroxides 过氧化物.
- Hydrogen is usually +1 but −1 in metal hydrides. In MnO₄⁻, x + 4(−2) = −1, so manganese is +7.
求MnO₄⁻中Mn的氧化数。已知O = −2。
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x + 4(−2) = −1，因此 x = +7。
Combine half-equations
- Mg → Mg²⁺ + 2e⁻ and Cl₂ + 2e⁻ → 2Cl⁻ contain equal electron amounts, so the electrons cancel.
- Mg is the reducing agent and is oxidised. Cl₂ is the oxidising agent and is reduced. Check atoms and total charge.
For Al reducing Cu²⁺, multiply Al → Al³⁺ + 3e⁻ by two and Cu²⁺ + 2e⁻ → Cu by three. The overall equation is 2Al + 3Cu²⁺ → 2Al³⁺ + 3Cu.
在 Mg + Cl₂ → Mg²⁺ + 2Cl⁻ 中，氧化剂是什么？
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Cl₂接受电子并被还原，因此它使镁氧化。
完成过程名称：失去电子的过程是_____。
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氧化是指失去电子且氧化数升高。
Explain two different group trends
- Down Groups 1/2, greater radius and shielding 屏蔽 weaken attraction to outer electrons. Electron loss becomes easier and reactivity generally rises.
- Small cations polarise carbonate/nitrate ions strongly. Their compounds are less thermally stable; stability generally rises down the group.
沿第1族向下增加屏蔽效应，使最外层电子更难失去。
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屏蔽效应增强和半径增大降低了对外层电子的吸引力，使其更容易失去。
Separate observations from explanations
- Group 2 hydroxide solubility rises down the group, while sulfate solubility falls. These are solubility trends, not electron-loss equations.
- Flame colours come from excited electrons falling to lower levels. Sodium gives yellow, potassium lilac, calcium brick-red and barium apple-green.
“The oxidising agent loses electrons” is false. It accepts electrons and is itself reduced.
Use oxidation-number sums, electron balance and a specific particle model; do not use “more reactive” as its own explanation.
哪两个关于第2族的趋势是正确的？
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氢氧化物和硫酸盐的溶解度趋势相反。小阳离子对阴离子的极化作用更强；砖红色是钙的特征焰色。