• # question_answer The atomic number of vanadium (V), chromium (Cr), manganese (Mn) and iron (Fe) are respectively 23, 24, 25 and 26 which one of these may be expected to have the highest second ionization enthalpy [AIEEE 2003] A) V B) Cr C) Mn D) Fe

$V=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{3}}4{{s}^{2}}$ $Cr=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{5}}4{{s}^{1}}$ $Mn=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{5}}4{{s}^{2}}$ $Fe=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{6}}4{{s}^{2}}$ In second ionization enthalpy $C{{r}^{+}}$ has exact half filled d-sub shell.