(a). Why `IE_1` of `Zn`, Cd and Hg are very high?
(b). The relative difference in IE of any two consecutive d-bloch elements is smaller than those of s and p-block elements.
(c). `IE_2` is usually very high for `Cr` and `Cu`. Why?

Explanation

(a). It is due to completely filled and stable configuration, i.e., `(n-1)d^(10)ns^(2)` configuration.
(b). This is because they involve gradual filling up of inner d-orbitals due to which increase in nuclear charge is partly cancelled by sheilding effect provided by inner d-electrons.
(c). This is because after the removal of first electron Cr and Cu acquire a stable configuration `(d^(5) and d^(10))` and the removal of second electron is very difficult.
(i). `Cr(3d^(5)4s^(1))toCr^(c+)(3d^(5))+e^(e-)` ....`IE_1`
`Cr^(c+)(3d^5)toCr^(2+)(3d^4)+e^(c-)` ...`IE_2`
`(becauseIE_2gtgtIE_1)`
(ii). `Cu(3d^(10)4s^(1))toCu^(c+)(3d^(10))+e^(c-)` ....`IE_1`
`Cu^(c+)(3d^(10))toCu^(2+)(3d^9)+e^(c-)` .....`IE_2`. `(becauseIE_2gtgtIE_1)`