Oxygen

Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds.

What the numbers say

At standard temperature and pressure Oxygen is a gas, sitting in period 2, group 16 of the p-block.

Its melting point of 54 K (-219 °C) is the 106th highest of the 110 elements with a measured value — among the lowest-melting elements.

At 0.001 g/cm³ it is the 92nd densest of 96 elements with a quoted density.

In the solid state it takes a base-centered monoclinic structure.

It is reported in 4 oxidation states (-2, -1, 1, 2), which sets how many distinct compounds and phases it can form.

First identified in 1774.

Crystal structure

Where oxygen shows up in engineering materials

1 entry in the materials library names it directly:

• Zirconia Y-TZP (3Y) — Oxide ceramic

Crystallographic examples

Oxygen or one of its compounds is a textbook example for these crystal systems:

• Cubic (isometric) — Cu, Al, Fe-α (BCC), NaCl, diamond, spinel MgAl₂O₄
• Trigonal (rhombohedral) — α-quartz, calcite CaCO₃, Bi, corundum Al₂O₃
• Triclinic — Kaolinite, albite, CuSO₄·5H₂O

Check it against computed structures

The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing O — with DFT formation energy, hull stability and band gap where the provider publishes them.