Chemistry - Complete d-block Question with Solution | TestHub

${\mathrm{Sc}}^{3+}(\mathrm{Z}=18):1s^2,2s^2{p}^6,3s^2{p}^6{d}^0,4s^0$; no unpaired electron. ${\mathrm{Cu}}^{+}(\mathrm{Z}=28):1s^2,2s^2{p}^6,3s^2{p}^6{d}^{10},4s^0$; no unpaired electron. $${\mathrm{Ni}}^{2+}(\mathrm{Z}=26):1s^2,2s^2{p}^6,3s^2{p}^6{d}^8,4s^0$$ unpaired electrons are present. $${\mathrm{Ti}}^{3+}(\mathrm{Z}=19):1s^2,2s^2{p}^6,3s^2{p}^6{d}^1,4s^0\text{; }$$ unpaired electron is present $${\mathrm{Co}}^{2+}(\mathrm{Z}=25):1s^2,2s^2{p}^6,3s^2{p}^6{d}^7,4s^0\text{; }$$ unpaired electrons are present So from the given options the only correct combination is ${\mathrm{Ni}}^{2+}$ and ${\mathrm{Ti}}^{3+}$.