Q. The atomic numbers 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 ionisation enthalpy?
A) V
B) Cr
C) Mn
D) Fe
Explanation
(b)
Cr :[Ar]
[table] $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | | $\upharpoonleft$ [/table]
$3d^{5}$ $4s^{1}$
${Cr}^{+}$:[Ar]
[table] $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | | $\upharpoonleft$ [/table]
$3d^{5}$ $4s^{0}$
This is stable EC, hence formation of ${Cr}^{2 +}$ by second IP requires maximum enthalpy.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.