## Chemistry: The Central Science (13th Edition)

For an electron in $n=3$, $$Z_{eff}(Mg)\lt Z_{eff}(P)\lt Z_{eff}(K)\lt Z_{eff}(Ti)\lt Z_{eff}(Rh)$$
We know that the effective nuclear charge $Z_{eff}$ for an electron would increase from left to right in a row in the periodic table, for the increase in nuclear charge. Therefore, - Row 3: $Z_{eff}(P)\gt Z_{eff}(Mg)$ - Row 4: $Z_{eff}(Ti)\gt Z_{eff}(K)$ Also, as we go down in the periodic table, the nuclear charge would dramatically increase, while the screening effect is almost the same for electrons in $n=3$, since the number of electrons in $n=1,2, 3$ stays the same. So, the effective nuclear charge would increase as we go down. Therefore, for an electron in $n=3$, $$Z_{eff}(Mg)\lt Z_{eff}(P)\lt Z_{eff}(K)\lt Z_{eff}(Ti)\lt Z_{eff}(Rh)$$