Question:
Why first ionisation enthalpy of Cr is lower than that of Zn?
Solution:
First ionisation enthalpy of Cr is lower than that of Zn. If we see the electronic configuration of Cr and Zn
Cr – [Ar] 3d5 4s1
Zn – [Ar] 3d10 4s2
Removing an electron from a half-filled 4s orbital requires lesser energy than removing an electron from a filled stable 4s orbital.