Chemical formulae · 化学式
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| chemical formula/ˈkemɪkl ˈfɔːmjʊlə/ | 化学式 | huà xué shì |
| subscript/ˈsʌbskrɪpt/ | 下标 | xià biāo |
| valency/ˈveɪlənsi/ | 化合价 | huà hé jià |
The shorthand of chemistry
- Writing "two hydrogen atoms joined to one oxygen atom" every time would be exhausting.
- Chemists use formulae — a compact code for what a substance is made of.
化学的速记
- 每次都写"两个氢原子连到一个氧原子"会很累人。
- 化学家使用化学式(formulae)——一种紧凑的代码,表示一种物质由什么构成。
Formula writing route · 书写化学式的步骤
Follow charges or valencies to a neutral chemical formula. · 遵循电荷或化合价得出中性化学式。
How many hydrogen atoms are in one molecule of H₂O? · 一个水分子 H₂O 中有多少个氢原子？
The subscript 2 means two hydrogen atoms. · 下标 2 表示有两个氢原子。
The small number that shows how many atoms of an element are present is the . · 显示某元素原子数量的数字是。
Subscripts give atom counts in a formula. · 下标给出了化学式中的原子数量。
Reading a formula
- A chemical formula 化学式 shows the elements and how many atoms of each.
- The small subscript 下标 number gives the count: H₂O = 2 hydrogen + 1 oxygen.
For an ionic compound, the ion charges cross over to give the formula
读一个化学式
- 一个化学式(chemical formula)显示元素以及每种有多少原子。
- 小的下标(subscript)数字给出数量:H₂O = 2 个氢 + 1 个氧。
对一个离子化合物,离子电荷交叉以给出化学式
Atoms combine in fixed ratios because of their: · 原子按照固定比例结合是因为它们的：
Valency sets how many bonds an atom forms. · 化合价决定了原子形成的键的数量。
Why formulae are fixed
- Atoms combine in fixed ratios set by their combining power (valency 化合价).
- For example, hydrogen has valency 1 and oxygen 2, so water is H₂O — not HO.
为什么化学式是固定的
- 原子以由它们的化合价(combining power / valency)设定的固定比例结合。
- 例如,氢有化合价 1 而氧有 2,所以水是 H₂O——不是 HO。
How many oxygen atoms are in Ca(OH)₂? · Ca(OH)₂ 中有多少个氧原子？
The bracket subscript 2 applies to OH, giving 2 O. · 括号下的下标 2 适用于 OH，因此有 2 个 O。
How many atoms in total are in CaCO₃? · CaCO₃ 中总共有多少个原子？
1 Ca + 1 C + 3 O = 5 atoms. · 1 个 Ca + 1 个 C + 3 个 O = 5 个原子。
Brackets in formulae
- Brackets group atoms that repeat: Ca(OH)₂ means one calcium and two OH groups.
- So Ca(OH)₂ contains 1 Ca, 2 O and 2 H.
Worked example. How many atoms are in CaCO₃? One calcium, one carbon, and three oxygen = 5 atoms in total. The subscript 3 applies only to the oxygen.
化学式中的括号
- 括号把重复的原子分组:Ca(OH)₂ 意思是一个钙和两个 OH 基团。
- 所以 Ca(OH)₂ 含有 1 个 Ca、2 个 O 和 2 个 H。
例题。 CaCO₃ 中有多少个原子?一个钙、一个碳和三个氧 = 总共 5 个原子。下标 3 只应用于氧。
You've got it
- a formula shows which elements and how many atoms of each (subscripts)
- atoms combine in fixed ratios set by their valency
- brackets group repeating units: Ca(OH)₂ has 2 O and 2 H
你掌握了
- 一个化学式显示哪些元素以及每种多少原子(下标)
- 原子以由它们的化合价设定的固定比例结合
- 括号把重复的单元分组:Ca(OH)₂ 有 2 个 O 和 2 个 H