The correct order of first \((\Delta_{\mathrm{i}} \mathrm{H}_{1})\) and second \((\Delta_{\mathrm{i}} \mathrm{H}_{2})\) ionisation enthalpy values of cr and Mn are : A. \(\Delta_{\mathrm{i}} \mathrm{H}_{1}: \mathrm{Cr}>\mathrm{Mn}\) B. \(\Delta_{\mathrm{i}} \mathrm{H}_{2}: \mathrm{Cr}>\mathrm{Mn}\) C. \(\Delta_{\mathrm{i}} \mathrm{H}_{1}: \mathrm{Mn}>\mathrm{Cr}\) D. \(\Delta_{\mathrm{i}} \mathrm{H}_{2}: \mathrm{Mn}>\mathrm{Cr}\) Choose the correct answer from the options given below :

JEE Main · 2026 · 06 Apr 2026 · Shift 2 · Classification of Elements and Periodicity

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

Δ_{i} H_{2} : Cr > Mn

Δ_{i} H_{1} : Mn > Cr

Δ_{i} H_{2} : Mn > Cr

Choose the correct answer from the options given below :

Answer: (B)

With configurations

Cr : [Ar] 3 d^{5} 4 s^{1}

and

Mn : [Ar] 3 d^{5} 4 s^{2}

, the first electron leaves the

4 s

orbital; chromium's stable half-filled

3 d^{5} 4 s^{1}

arrangement lowers its first ionisation enthalpy, so

Mn > Cr

for

Δ_{i} H_{1}

. After one removal,

C r^{+}

[Ar] 3 d^{5}

(a stable half-filled set) while

M n^{+}

[Ar] 3 d^{5} 4 s^{1}

; stripping the second electron from the stable

C r^{+}

demands more energy, so

Cr > Mn

for

Δ_{i} H_{2}

. The correct statements are

Δ_{i} H_{2} : Cr > Mn

and

Δ_{i} H_{1} : Mn > Cr

JEE Main · 2026 · 06 Apr 2026 · Shift 2 · Single correct option