Oxygen (symbol O, atomic number 8) is the reactive gas animals breathe and the most abundant element in the Earth's crust. It is classified as a reactive nonmetal and sits in group 16, period 2 of the periodic table.
Overview
Oxygen is the chemical element with atomic number 8 and the symbol O. With a standard atomic weight of 15.999, it is a reactive nonmetal. In the periodic table it occupies group 16 and period 2, and under standard conditions it is normally a gas. Oxygen is the reactive gas animals breathe and the most abundant element in the Earth's crust.
Atomic structure
An atom of Oxygen has 8 protons in its nucleus and, when neutral, 8 electrons arranged in the configuration [He] 2s2 2p4. Its standard atomic weight of 15.999 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Oxygen was discovered in 1774 by Carl Wilhelm Scheele, Joseph Priestley. It follows Nitrogen (N) and precedes Fluorine (F) in order of atomic number.
| Atomic number | 8 |
|---|---|
| Symbol | O |
| Atomic mass | 15.999 |
| Category | Reactive nonmetal |
| Group | 16 |
| Period | 2 |
| Electron configuration | [He] 2s2 2p4 |
| Phase at STP | Gas |
| Discovered | 1774 (Carl Wilhelm Scheele, Joseph Priestley) |