Assertion: Cr has higher melting point than Mn.

Reason: More the number of unpaired electrons, higher is the melting point.

Assertion and Reason both are correct statements and reason is the correct explanation for assertion.

Transition metals have very high melting and boiling points. In each series the melting point of these metals rise to a maximum value and then decrease with increase in atomic number.

More the number of unpaired electrons higher is the melting point. When there is no unpaired electrons, the melting points are low as for Zn, Cd and Hg.