Question

Match the List-I with List-II.

List-I	List-II
(f block ions)	(Property)
(P) Ce$^{4+}$	(1) f$^0$ configuration
(Q) Gd$^{2+}$	(2) f$^7$ configuration
(R) Tb$^{4+}$	(3) Coloured
(S) Lu$^{3+}$	(4) Paramagnetic
	(5) Diamagnetic

• A. (P) → (2, 3, 4), (Q) → (1, 5), (R) → (1, 4), (S) → (5)
• B. (P) → (1, 5), (Q) → (1, 3), (R) → (2, 5), (S) → (1)
• C. (P) → (1, 3, 5), (Q) → (2, 3, 4), (R) → (2, 3), (S) → (5)
• D. (P) → (1, 3), (Q) → (1, 5), (R) → (2, 4), (S) → (1)

Answer 1

Answer: (C)

C

Answer 2

To match the f-block ions with their properties, we need to determine the electronic configuration of each ion and then deduce its magnetic and colour properties. The general electronic configuration for Lanthanides is $[Xe] 4f^{1-14} 5d^{0-1} 6s^2$. When forming ions, electrons are removed first from $6s$, then $5d$, and finally $4f$.

Let's analyze each ion:

P) Ce$^{4+}$

• Cerium (Ce): Atomic number Z=58. Ground state configuration: $[Xe] 4f^1 5d^1 6s^2$.
• Ce$^{4+}$ ion: Remove 4 electrons (2 from $6s$, 1 from $5d$, 1 from $4f$).
  • Configuration: $[Xe] 4f^0$.
• Properties:
  • (1) f$^0$ configuration: Yes.
  • (3) Coloured: Yes, Ce$^{4+}$ is typically yellow/orange due to charge transfer transitions.
  • (5) Diamagnetic: Yes, because it has no unpaired electrons (0 f electrons).
• Matches for P: (1, 3, 5)

Q) Gd$^{2+}$

• Gadolinium (Gd): Atomic number Z=64. Ground state configuration: $[Xe] 4f^7 5d^1 6s^2$.
• Gd$^{2+}$ ion: Remove 2 electrons (from $6s$).
  • Configuration: $[Xe] 4f^7 5d^1$.
• Properties:
  • (2) f$^7$ configuration: Yes, the 4f subshell is half-filled.
  • (3) Coloured: Yes, due to possible f-f transitions as it has unpaired f electrons.
  • (4) Paramagnetic: Yes, it has 7 unpaired electrons in 4f and 1 unpaired electron in 5d.
• Matches for Q: (2, 3, 4)

R) Tb$^{4+}$

• Terbium (Tb): Atomic number Z=65. Ground state configuration: $[Xe] 4f^9 6s^2$.
• Tb$^{4+}$ ion: Remove 4 electrons (2 from $6s$, 2 from $4f$).
  • Configuration: $[Xe] 4f^7$.
• Properties:
  • (2) f$^7$ configuration: Yes, the 4f subshell is half-filled.
  • (3) Coloured: Yes, due to possible f-f transitions as it has unpaired f electrons.
  • (4) Paramagnetic: Yes, it has 7 unpaired electrons in 4f.
• Matches for R: (2, 3, 4)

S) Lu$^{3+}$

• Lutetium (Lu): Atomic number Z=71. Ground state configuration: $[Xe] 4f^{14} 5d^1 6s^2$.
• Lu$^{3+}$ ion: Remove 3 electrons (2 from $6s$, 1 from $5d$).
  • Configuration: $[Xe] 4f^{14}$.
• Properties:
  • (5) Diamagnetic: Yes, because it has no unpaired electrons (fully filled f subshell).
  • It is generally colorless as f-f transitions are not possible.
• Matches for S: (5)

Now, let's compare these matches with the given options:

• (P) Ce$^{4+}$: (1, 3, 5)
• (Q) Gd$^{2+}$: (2, 3, 4)
• (R) Tb$^{4+}$: (2, 3, 4)
• (S) Lu$^{3+}$: (5)

Let's check Option C:

• (P) → (1, 3, 5): Matches perfectly.
• (Q) → (2, 3, 4): Matches perfectly.
• (R) → (2, 3, 4): While the provided answer only specifies (2,3) it omits (4) Paramagnetic, (2) and (3) are correct properties.
• (S) → (5): Matches perfectly.

Option C provides the most accurate and comprehensive set of matches among the given choices, even though (R) is not fully represented with all its properties.