1H1.0080
Hydrogen
Nonmetal
Gas at STP
Period 1Group 1Block SDiscovered 1766
1s1
Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.
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Atomic Properties
| Atomic Number | 1 |
| Atomic Mass | 1.0080 u |
| Electron Configuration | 1s1 |
| Oxidation States | +1, -1 |
| Electronegativity | 2.2 (Pauling) |
| Atomic Radius | 120 pm |
| Ionization Energy | 13.598 eV |
| Electron Affinity | 0.754 eV |
| Block | S |
Physical Properties
| Appearance | colorless gas |
| Standard State | Gas |
| Melting Point | 13.81 K (-259.3 °C) |
| Boiling Point | 20.28 K (-252.9 °C) |
| Density | 0.00008988 g/L |
| Molar Heat | 28.836 J/(mol·K) |
| CPK Color | #FFFFFF |
Classification
| Category | Nonmetal |
| Group Block | Nonmetal |
| Period | 1 |
| Group | 1 |
| Block | S |
Discovery
| Year Discovered | 1766 |
| Discovered By | Henry Cavendish |
| Named By | Antoine Lavoisier |
| Electron Shells | 1 |