8O15.999
Oxygen
Nonmetal
Gas at STP
Period 2Group 16Block PDiscovered 1774
[He]2s2 2p4
Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive nonmetal and oxidizing agent that readily forms compounds (notably oxides) with most elements. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium.
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Atomic Properties
| Atomic Number | 8 |
| Atomic Mass | 15.999 u |
| Electron Configuration | [He]2s2 2p4 |
| Oxidation States | -2 |
| Electronegativity | 3.44 (Pauling) |
| Atomic Radius | 152 pm |
| Ionization Energy | 13.618 eV |
| Electron Affinity | 1.461 eV |
| Block | P |
Physical Properties
| Standard State | Gas |
| Melting Point | 54.36 K (-218.8 °C) |
| Boiling Point | 90.2 K (-182.9 °C) |
| Density | 0.001429 g/L |
| CPK Color | #FF0D0D |
Classification
| Category | Nonmetal |
| Group Block | Nonmetal |
| Period | 2 |
| Group | 16 |
| Block | P |
Discovery
| Year Discovered | 1774 |
| Discovered By | Carl Wilhelm Scheele |
| Named By | Antoine Lavoisier |
| Electron Shells | 2, 6 |