Block s elements
The s-block consists of groups 1 and 2 (the alkali metals and alkaline earth metals) plus hydrogen and helium. Elements here have their outermost electron in an s-orbital, making them highly reactive (except helium).
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| No. | Symbol | Element | Atomic weight (u) | Density (g/cm³) | Melting point (K) | Boiling point (K) | Electronegativity | Discovered |
|---|---|---|---|---|---|---|---|---|
| 1 | H | Hydrogen | 1.0079 | 0.08988 | 13.99 | 20.271 | 2.2 | 1766 |
| 2 | He | Helium | 4.0026 | 0.1786 | 0.95 | 4.222 | - | 1868 |
| 3 | Li | Lithium | 6.938 | 0.534 | 453.65 | 1603 | 0.98 | 1817 |
| 4 | Be | Beryllium | 9.01218 | 1.85 | 1560 | 2742 | 1.57 | 1798 |
| 11 | Na | Sodium | 22.9898 | 0.968 | 370.944 | 1156.09 | 0.93 | 1807 |
| 12 | Mg | Magnesium | 24.304 | 1.738 | 923 | 1363 | 1.31 | 1755 |
| 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 |
| 38 | Sr | Strontium | 87.621 | 2.64 | 1050 | 1650 | 0.95 | 1787 |
| 55 | Cs | Cesium | 132.905 | 1.93 | 301.7 | 944 | 0.79 | 1860 |
| 56 | Ba | Barium | 137.328 | 3.51 | 1000 | 2118 | 0.89 | 1772 |
| 87 | Fr | Francium | 223 | 1.87 | 300 | 950 | 0.79 | 1939 |
| 88 | Ra | Radium | 226 | 5.5 | 1233 | 2010 | 0.9 | 1898 |