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:

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

Answer 1

The Correct Option is D

To solve this question, we need to determine the number of unpaired electrons in each of the given elements and then arrange them in increasing order. The unpaired electron count is determined by the electronic configuration of each element.

1. Find the atomic numbers and electron configurations:
   • Scandium (Sc): Atomic number = 21, Configuration = [Ar] 3d¹ 4s²
   • Chromium (Cr): Atomic number = 24, Configuration = [Ar] 3d⁵ 4s¹
   • Vanadium (V): Atomic number = 23, Configuration = [Ar] 3d³ 4s²
   • Titanium (Ti): Atomic number = 22, Configuration = [Ar] 3d² 4s²
   • Manganese (Mn): Atomic number = 25, Configuration = [Ar] 3d⁵ 4s²
2. Count the number of unpaired electrons:
   • Sc (3d¹): 1 unpaired electron
   • Cr (3d⁵): 6 unpaired electrons (5 in 3d and 1 in 4s)
   • V (3d³): 3 unpaired electrons
   • Ti (3d²): 2 unpaired electrons
   • Mn (3d⁵): 5 unpaired electrons
3. Arrange the elements in increasing order based on their unpaired electrons:
   • Sc (1 unpaired electron), Ti (2 unpaired electrons), V (3 unpaired electrons), Mn (5 unpaired electrons), Cr (6 unpaired electrons)

Thus, the increasing order of elements based on the number of unpaired electrons is:

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

Correct Answer: (A) < (D) < (C) < (E) < (B)

Answer 2

The electronic configurations and the number of unpaired electrons for each element are as follows:

Sc: \([ \text{Ar} ] 4s^2 3d^1 \quad (1 \text{ unpaired electron})\)
Cr: \([ \text{Ar} ] 4s^1 3d^5 \quad (6 \text{ unpaired electrons})\)
V: \([ \text{Ar} ] 4s^2 3d^3 \quad (3 \text{ unpaired electrons})\)
Ti: \([ \text{Ar} ] 4s^2 3d^2 \quad (2 \text{ unpaired electrons})\)
Mn: \([ \text{Ar} ] 4s^2 3d^5 \quad (5 \text{ unpaired electrons})\)

Arranging them in increasing order of unpaired electrons, we get:

\(\text{Sc (A)} < \text{Ti (D)} < \text{V (C)} < \text{Mn (E)} < \text{Cr (B)}\)