Technetium

Technetium is a chemical element with the symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive, none of which is stable other than the fully ionized state of 97Tc.

What the numbers say

At standard temperature and pressure Technetium is a solid, sitting in period 5, group 7 of the d-block.

Its melting point of 2430 K (2157 °C) is the 11th highest of the 110 elements with a measured value — mid-range among the elements.

At 11.5 g/cm³ it is the 23rd densest of 96 elements with a quoted density.

Pauling electronegativity is 1.9. Paired with oxygen (3.44) that is a difference of 1.54, which puts the bond polar covalent — oxides here tend to be semiconducting or refractory rather than salt-like.

In the solid state it takes a simple hexagonal structure — hexagonal packing offers few easy slip systems, so properties are anisotropic and formability is limited.

It is reported in 9 oxidation states (-3, -1, 1, 2, 3, 4, 5, 6, 7), which sets how many distinct compounds and phases it can form.

First identified in 1937.

Crystal structure

Check it against computed structures

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