Answer:
Transition metals
Step-by-step explanation:
The transition metals are usually harder than other metals such as the alkali metal, lanthanide series metals and the alkaline earthmetals.
The reason for this is because they have a stronger metallic bonding between their atom.
Hardness is a physical property which is attributed to intermolecular forces and the atomic arrangement
The transition metals are found in the d - block on the periodic table.
They have a d-orbirtal which confers extra electrons and higher degree of stability to the atom. The d-orbirtal provides more delocalized electrons for the metallic bonds formed.