JEE Main 2026 Apr 6 Shift 2, Chemistry Q10: Periodicity In Atomic Properties

JEE Main2026Apr 6, Shift 2Chemistry

The correct order of first ( $Δ_{i} H_{1}$ ) and second ( $Δ_{i} H_{2}$ ) ionisation enthalpy values of Cr and Mn are:

A. $Δ_{i} H_{1} : Cr > Mn$

B. $Δ_{i} H_{2} : Cr > Mn$

C. $Δ_{i} H_{1} : Mn > Cr$

D. $Δ_{i} H_{2} : Mn > Cr$

Choose the correct answer from the options given below:

A
A and B only
B
B and C only
C
A and D only
D
C and D only

Solution

Configurations: Cr $= [Ar] 3 d^{5} 4 s^{1}$ , Mn $= [Ar] 3 d^{5} 4 s^{2}$ .

First IE. Mn loses one of two $4 s$ electrons against a stable half-filled $3 d^{5}$ core, but the paired $4 s$ in Mn has slightly higher penetration than Cr's lone $4 s$ . Experimentally $IE_{1} (Mn) > IE_{1} (Cr)$ — statement C holds.

Second IE. After losing one electron, Cr $^{+}$ becomes $[Ar] 3 d^{5}$ — a stable half-filled configuration — whereas Mn $^{+}$ becomes $[Ar] 3 d^{5} 4 s^{1}$ . Removing the next electron from Cr $^{+}$ disrupts the stable half-filled set, so $IE_{2} (Cr) > IE_{2} (Mn)$ — statement B holds.

Correct: B and C.

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JEE Main 2026 Apr 6 Shift 2, Chemistry Q10: Periodicity In Atomic Properties

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