JEE Main · 2022 · 28 Jul 2022 · Shift 2 · d and f Block Elements

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Which of the following pair is not isoelectronic species?
(At. no. Sm, 62; Er, 68: Yb, 70: Lu, 71; Eu, 63: Tb, 65; Tm, 69)
  1. (A) and
  2. (B) and
  3. (C) and
  4. (D) and ✓ Correct

Answer: (D)

Solution

Isoelectronic species have the same number of electrons. Let's calculate:
  • : 65 - 2 = 63 electrons
  • : 69 - 4 = 65 electrons

Since 63 ≠ 65, and are not isoelectronic. All other pairs have equal electron counts.

JEE Main · 2022 · 28 Jul 2022 · Shift 2 · Single correct option

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