Hydrogen (symbol H, atomic number 1) is the lightest and most abundant element in the universe, the fuel of stars and the basis of water. It is classified as a reactive nonmetal and sits in group 1, period 1 of the periodic table.
Overview
Hydrogen is the chemical element with atomic number 1 and the symbol H. With a standard atomic weight of 1.008, it is a reactive nonmetal. In the periodic table it occupies group 1 and period 1, and under standard conditions it is normally a gas. Hydrogen is the lightest and most abundant element in the universe, the fuel of stars and the basis of water.
Atomic structure
An atom of Hydrogen has 1 proton in its nucleus and, when neutral, 1 electron arranged in the configuration 1s1. Its standard atomic weight of 1.008 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Hydrogen was discovered in 1766 by Henry Cavendish. It is the first element, immediately followed by Helium (He).
| Atomic number | 1 |
|---|---|
| Symbol | H |
| Atomic mass | 1.008 |
| Category | Reactive nonmetal |
| Group | 1 |
| Period | 1 |
| Electron configuration | 1s1 |
| Phase at STP | Gas |
| Discovered | 1766 (Henry Cavendish) |