Alkali metals
The alkali metals (lithium, sodium, potassium, rubidium, cesium, francium) make up Group 1 of the periodic table. They are soft, silvery and so reactive that they are stored under oil to keep them away from air and water. They readily lose their single outer electron to form +1 ions, and they react vigorously with water to form alkaline hydroxides.
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| No. | Symbol | Element | Atomic weight (u) | Density (g/cm³) | Melting point (K) | Boiling point (K) | Electronegativity | Discovered |
|---|---|---|---|---|---|---|---|---|
| 3 | Li | Lithium | 6.938 | 0.534 | 453.65 | 1603 | 0.98 | 1817 |
| 11 | Na | Sodium | 22.9898 | 0.968 | 370.944 | 1156.09 | 0.93 | 1807 |
| 19 | K | Potassium | 39.0983 | 0.862 | 336.7 | 1032 | 0.82 | 1807 |
| 37 | Rb | Rubidium | 85.4678 | 1.532 | 312.45 | 961 | 0.82 | 1861 |
| 55 | Cs | Cesium | 132.905 | 1.93 | 301.7 | 944 | 0.79 | 1860 |
| 87 | Fr | Francium | 223 | 1.87 | 300 | 950 | 0.79 | 1939 |