| Alkali metal | Standard Atomic Weight (u) | Melting Point (K) | Boiling Point (K) | Density (g/cm3) | Electronegativity (Pauling) |
| Lithium | 6.941 | 453 | 1615 | 0.534 | 0.98 |
| Sodium | 22.990 | 370 | 1156 | 0.968 | 0.93 |
| Potassium | 39.098 | 336 | 1032 | 0.89 | 0.82 |
| Rubidium | 85.468 | 312 | 961 | 1.532 | 0.82 |
| Caesium | 132.905 | 301 | 944 | 1.93 | 0.79 |
| Francium | (223) | 295 | 950 | 1.87 | 0.70 |
The alkali metals are a series of elements forming Group 1 of the periodic table: lithium(Li), sodium(Na), potassium(K), rubidium (Rb), caesium (Cs), and francium(Fr).
The alkali metals, found in group 1 of the periodic table (formerly known as group IA), are very reactive metals that do not occur freely in nature. These metals have only one electron in their outer shell. Therefore, they are ready to lose that one electron in ionic bonding with other elements. As with all metals, the alkali metals are malleable, ductile, and are good conductors of heat and electricity. The alkali metals are softer than most other metals. Cesium and francium are the most reactive elements in this group. Alkali metals can explode if they are exposed to water.
| Z | Element | No. of electrons/shell |
|---|---|---|
| 1 | Hydrogen | 1 |
| 3 | Lithium | 2, 1 |
| 11 | Sodium | 2, 8, 1 |
| 19 | Potassium | 2, 8, 8, 1 |
| 37 | Rubidium | 2, 8, 18, 8, 1 |
| 55 | Caesium | 2, 8, 18, 18, 8, 1 |
| 87 | Francium | 2, 8, 18, 32, 18, 8, 1 |
Alkali metals are famous for their vigorous reactions with water, and these reactions become increasingly violent as one moves down the group. The reaction with water is as follows:
Alkali metal + water → Alkali metal hydroxide + hydrogen gas
With potassium as an example:
2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)
This is a video about how potassium and sodium react with water:
http://www.metacafe.com/watch/654142/exploding_sodium_and_potassium_in_water_chemical_demonstration/
