The atomic number of V, Cr, Mn and Fe are respectively 23, 24, 25 and 26.Which one of these may be expected to have the highest second ionisation enthalpy ?

Question

The atomic number of V, Cr, Mn and Fe are respectively 23, 24, 25 and 26.Which one of these may be expected to have the highest second ionisation enthalpy ? (A) V (B) Cr (C) Mn (D) Fe

Tardigrade Admin · Accepted Answer

Outer electronic configurations of V, Cr, Mn and Fe are as follows.

V (4 s^{2} 3 d^{3}), C r (4 s^{1} 3 d^{5}), M n (4 s^{2} 3 d^{5}), F e (4 s^{2} 3 d^{6})

Outer electronic configuration of uni-positive ions are

V^{+} (4 s^{1} 3 d^{3}), C r^{+} (3 d^{5}), M n^{+} (4 s^{1} 3 d^{5}), F e^{+} (4 s^{1} 3 d^{6})

Clearly, I.

E_{2}

of Cr will be highest as

C r^{+}

has exactly half filled

d

-subshell.

Q. The atomic number of V, Cr, Mn and Fe are respectively 23, 24, 25 and 26.Which one of these may be expected to have the highest second ionisation enthalpy ?

V

Cr

Mn

Fe

Outer electronic configurations of V, Cr, Mn and Fe are as follows. V(4s23d3),Cr(4s13d5),Mn(4s23d5),Fe(4s23d6) Outer electronic configuration of uni-positive ions are V+(4s13d3),Cr+(3d5),Mn+(4s13d5),Fe+(4s13d6) Clearly, I.E2​ of Cr will be highest as Cr+ has exactly half filled d-subshell.