What element has an r. m. m of 72

Germanium

Explanation:

The element Germanium is one with a relative molecular mass of 72. This corresponds to the mass number of this element.

Relative molecular mass of an element is the mass of a formula unit to that of a carbon-12 atom.

The chemical symbol of Germanium is Ge. It is a lustrous and hard metalloid belonging to the carbon group.

It was discovered by Clemens Alexander Winkler.