Oxygen

Element 8 on the periodic table, symbol O, group 16, period 2.

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.

Properties

Atomic Number: 8
Atomic Mass: 15.9990 u
Group: 16
Period: 2
Block: p-block
Category: Diatomic Non-Metal
State at 25 °C: Gas
Melting Point: 54.4 K · -218.8 °C
Boiling Point: 90.2 K · -183 °C
Density: 1.429 g/L
Atomic Radius: 60 pm
Electronegativity: 3.44
Oxidation States: -2
Abundance in Crust: 4.61e+5 mg/kg
Discovered: 1774
Discovered By: Carl Wilhelm Scheele

Electron Configuration

[He] 2s2 2p4

1s2 2s2 2p4

Ionisation Energies (kJ/mol)

1. 1,313.9
2. 3,388.3
3. 5,300.5
4. 7,469.2
5. 10,989.5
6. 13,326.5
7. 71,330
8. 84,078

Elements near Oxygen

Elements in the same group share the number of outer electrons and behave in similar ways. Elements in the same period share a shell, so they change steadily from left to right.