Question

Why are metals like chromium and molybdenum very hard?​

Answer 1

Hardness

The hardness of a metal denotes its ability to withstand corrosion, high boiling points and resist deformity under pressure.

Chromium and molybdenum are hard metals because they posses such characteristics.

Their interaction with other metals like steel is strong because of the presence of six unpaired electrons in the 3d and 4s sub-shell for chromium and 4d, 5s sub-shells in molybdenum.

The harness of metals is measured using different scales like the Mohs scale of mineral hardness.

On Mohs scale chromium has a a value of 8.5 and molybdenum has 5.5, which indicate they are harder than many metals.

Hope this helps.