定义Definition
钡是原子序数为 56 的元素，符号 Ba，属于第二族碱土金属。钡是银白色活泼金属，与冷水剧烈反应。可溶性钡盐有毒，而硫酸钡几乎不溶，可作“钡餐”用于消化道 X 射线造影。钡的化合物使火焰呈黄绿色。
Barium is the element with atomic number 56 and symbol Ba, a group 2 alkaline earth metal. It is a reactive silvery metal that reacts vigorously with cold water. Soluble barium salts are toxic, but barium sulfate is almost insoluble and is used as a 'barium meal' for X-ray imaging of the digestive tract. Barium compounds colour flames apple green.
元素数据Element data
| 原子序数Atomic number | 56 |
|---|---|
| 元素符号Symbol | Ba |
| 相对原子质量Standard atomic weight | 137.33 |
| 电子排布Electron configuration | [Xe] 6s² |
| 族 / 周期 / 区Group / period / block | 2 / 6 / s |
| 电负性（鲍林）Electronegativity (Pauling) | 0.89 |
| 常见氧化态Common oxidation states | +2 |
硫酸根的检验Test for sulfate
向用稀盐酸酸化的溶液中加入 BaCl₂ 溶液，生成不溶于酸的白色 BaSO₄ 沉淀，说明含有 SO₄²⁻：Ba²⁺ + SO₄²⁻ → BaSO₄(s)。先酸化是为了排除 CO₃²⁻ 和 SO₃²⁻ 的干扰。
Adding BaCl₂ solution to a solution acidified with dilute hydrochloric acid gives a white precipitate of BaSO₄, insoluble in acid, if SO₄²⁻ is present: Ba²⁺ + SO₄²⁻ → BaSO₄(s). Acidifying first removes interference from CO₃²⁻ and SO₃²⁻.
第二族中的位置Its place in group 2
Ba 是第二族中（除放射性的镭外）最活泼的金属，Ba(OH)₂ 溶解度最大、碱性最强，BaSO₄ 溶解度最小，BaCO₃ 热分解温度最高。
Apart from radioactive radium, barium is the most reactive group 2 metal: Ba(OH)₂ is the most soluble and most strongly alkaline hydroxide, BaSO₄ the least soluble sulfate, and BaCO₃ the hardest carbonate to decompose.
化学性质Chemical properties
与水反应：Ba + 2H₂O → Ba(OH)₂ + H₂
Reacts with water: Ba + 2H₂O → Ba(OH)₂ + H₂
Ba²⁺ + SO₄²⁻ → BaSO₄（白色沉淀）
Ba²⁺ + SO₄²⁻ → BaSO₄ (white precipitate)
年表Timeline
- 1808
戴维用电解法首次制得金属钡
Davy first isolates barium metal by electrolysis