JEE Main · 2024 · Shift-IImediumDNF-004

Arrange the following elements in the increasing order of number of unpaired electrons in it. (A) Sc (B) Cr (C) V (D)…

d & f-Block Elements · Class 12 · JEE Main Previous Year Question

Question

Arrange the following elements in the increasing order of number of unpaired electrons in it.

(A) Sc (B) Cr (C) V (D) Ti (E) Mn

Choose the correct answer from the options given below:

Options
  1. a

    (A) < (D) < (C) < (B) < (E)

  2. b

    (C) < (E) < (B) < (A) < (D)

  3. c

    (A) < (D) < (C) < (E) < (B)

  4. d

    (B) < (C) < (D) < (E) < (A)

Correct Answerc

(A) < (D) < (C) < (E) < (B)

Detailed Solution

Ground state unpaired electrons:

| Element | Config | Unpaired e⁻ | |---------|--------|-------------| | Sc (A, Z=21) | [Ar] 3d14s23d^1 4s^2 | 1 | | Ti (D, Z=22) | [Ar] 3d24s23d^2 4s^2 | 2 | | V (C, Z=23) | [Ar] 3d34s23d^3 4s^2 | 3 | | Mn (E, Z=25) | [Ar] 3d54s23d^5 4s^2 | 5 | | Cr (B, Z=24) | [Ar] 3d54s13d^5 4s^1 | 6 |

Key: Cr has the special half-filled 3d54s13d^5 4s^1 configuration → 6 unpaired electrons (more than Mn's 5).

Increasing order: Sc(1) < Ti(2) < V(3) < Mn(5) < Cr(6) (A)<(D)<(C)<(E)<(B)(A) < (D) < (C) < (E) < (B)

Answer: Option (3)

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