The elements with maximum and minimum melting points in First and second transition series respectively are
 

Melting point is max. for Cr and minimum for Cd.
 

Electronic configuration is as follows:
         Cr =[Ar]3d⁵4s¹ , Cd =[Kr]4d¹⁰5s²
Cr has 5 unpaired electrons & has strong metallic bonding due to all unpaired electrons of 'S' and 'p' orbitals. So 'Cr' has high M.P.

In case of 'Cd' has no unpaired electrons so no participating in bonding.

Therefore minimum M.P.in 2^nd transition series.