Question

Second ionization energies of chromium and copper are larger than those of their neighbouring elements $(V,Mn,Ni,Zn)$. It is due to the fact that

• A. Second electron in each case is removed from $4s$ orbital
• B. Second electron is removed from stable half-filled $3d$ sub-orbit in case of chromium and from stable completely filled $3d$ sub-robit in case of copper
• C. Electrode potential of these elements ( $Cr$ and $Cu$ ) are higher than those of their neighbouring elements
• D. Their atomic radii are different due to screening effect

Answer 1

Answer: (B)

Both are stable configuration and removal of next electron requires very high energy. Thus, second IE is very high
$V^{+}[Ar]3d^{3}4s^1$ ) Second electron is removed for
$M{n}^{+}[Ar]3d^{5}4s^1$ ) $4s$ subshell, thus, second IE is
$N{i}^{+}[Ar]3d^{8}4s^1$ ) low
$Z{n}^{+}[\text{Ar}]3d^{10}4s^1)$