Match the elements given in List-I with

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Target Exam

CUET

Subject

Chemistry

Chapter

Inorganic: D and F Block Elements

Question:

Match the elements given in List-I with electronic configuration given in List-II

List-I Element	List-II Electronic configuration
(A) Cerium	(I) $[Xe] 4f^{12} 6s^2$
(B) Erbium	(II) $[Rn] 5f^7 6d^1 7s^2$
(C) Uranium	(III) $[Xe] 4f^1 5d^1 6s^2$
(D) Curium	(IV) $[Rn] 5f^3 6d^1 7s^2$

Choose the correct answer from the options given below:

Options:

(A)-(I), (B)-(II), (C)-(III), (D)-(IV)

(A)-(III), (B)-(I), (C)-(IV), (D)-(II)

(A)-(I), (B)-(II), (C)-(IV), (D)-(III)

(A)-(III), (B)-(IV), (C)-(I), (D)-(II)

Correct Answer:

(A)-(III), (B)-(I), (C)-(IV), (D)-(II)

Explanation:

The correct answer is Option (2) → (A)-(III), (B)-(I), (C)-(IV), (D)-(II)

List-I Element	List-II Electronic configuration
(A) Cerium	(III) $[Xe] 4f^1 5d^1 6s^2$
(B) Erbium	(I) $[Xe] 4f^{12} 6s^2$
(C) Uranium	(IV) $[Rn] 5f^3 6d^1 7s^2$
(D) Curium	(II) $[Rn] 5f^7 6d^1 7s^2$

(A) Cerium (Ce, Z=58): As the first element of the lanthanide series after Lanthanum, it retains one electron in the $5d$ orbital.
- Configuration: $[Xe] 4f^1 5d^1 6s^2$ → (III)
(B) Erbium (Er, Z=68): This is a later lanthanide. By this point, the $4f$ orbital is being filled, and there are no electrons in the $5d$ orbital for the ground state.
- Configuration: $[Xe] 4f^{12} 6s^2$ → (I)
(C) Uranium (U, Z=92): An actinide. It has three electrons in the $5f$ orbital and one in the $6d$ orbital.
- Configuration: $[Rn] 5f^3 6d^1 7s^2$ → (IV)
(D) Curium (Cm, Z=96): This is a key exception in the actinide series. To achieve a stable half-filled $5f^7$ configuration, one electron resides in the $6d$ orbital.
- Configuration: $[Rn] 5f^7 6d^1 7s^2$ → (II)