Zn, Cd and Hg are sometimes not considered as transition elements. Give reasons with electronic configuration.

Explanation

`Z=117=[Rn]5f^(14)6d^(10)7s^(2)p^(5)`
Principle quantum number of the valence shell is 7. So it belongs to `7^(th)` period, p-block Group number for Z=117 is = 10 +2 + 5 = 17, which is Halogen family
ii) `Z=120=["Unn"]8s^(2)`
Principal quantum number of valence shell is 8. So it belongs to 8th period, s-block. Group number for Z= 120 = number of e in valence shell=2
Thus it belongs to alkaline earth metals.