Select the correct statements:

Correct (l) very large difference, M. Pt. of Cr is 1920°C and that of Zn is 420°C.The melting points depends on the occupancy of the bonding and anti-bonding - molecular orbitals higher occupancy low M, Pt. Cr = 3d5,4S1. Energy of 3d and 4s are very close to each other and bands of 3s and 4s overlap. The composite band which can accommodate 12 valence e-'s metal atom will be half filled for Cr and completely filled for Zn.(2) In Cr, due to 5 unpaired e-'s, interatomic bonding is very strong, hence hard metal. In Hg, 3d subshell is fllled to the maximum capacity (5d10 6S2), these e-'s are not available for interatomic bonding and thus, bonding is very weak, hence Hg is a liquid at room temperature. Alternatively, if 5d and 6s bands overlap, the composite band can accommodate 12 valence e 's metal atom. Both bonding and anti-bonding are occupied in Hg and thus weak bonding and low M. Pt. (3) Sum of IE1+IE2+IE3+IE4 energies for Pt is lower than Ni.  (4) Sum of IE1+IE2 energies for Ni is lower than for Pt.