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NEET CHEMISTRYStructure of AtomMedium

Question

Which one of the following ions has electronic configuration [Ar]3d⁶? (At. no: Mn = 25, Fe = 26, Co = 27, Ni = 28)

A

Ni³⁺

B

Mn³⁺

C

Fe³⁺

D

Co³⁺

Step-by-Step Solution

The electronic configuration of an ion is determined by removing electrons from the outermost shell (4s) first, followed by the penultimate shell (3d).

  1. Cobalt (Co, Z=27): The neutral atom configuration is [Ar]3d74s2[Ar] 3d^7 4s^2 .
  2. Formation of Co³⁺: To form the +3 ion, 3 electrons are removed: 2 from the 4s orbital and 1 from the 3d orbital.
  • Co3+Co^{3+} configuration: [Ar]3d6[Ar] 3d^6.

Verification of other options:

  • Ni³⁺ (Z=28): Neutral is [Ar]3d84s2[Ar] 3d^8 4s^2. Removing 3 electrons gives [Ar]3d7[Ar] 3d^7.
  • Mn³⁺ (Z=25): Neutral is [Ar]3d54s2[Ar] 3d^5 4s^2. Removing 3 electrons gives [Ar]3d4[Ar] 3d^4.
  • Fe³⁺ (Z=26): Neutral is [Ar]3d64s2[Ar] 3d^6 4s^2. Removing 3 electrons gives [Ar]3d5[Ar] 3d^5 (half-filled, stable) .

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Structure of Atom. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYStructure of Atomfollowingelectronicconfiguration

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