MEDIUMMCQ SINGLENEET ChemistryPhysical ChemistryAtomic StructureIntro

[CBSE AIPMT 2015] The number of d-electrons in Fe²⁺ (Z = 26) is NOT equal to the number of electrons in which one of the following?

0.s-electrons in Mg (Z = 12)
1.p-electrons in Cl (Z = 17)
2.d-electrons in Fe (Z = 26)
3.p-electrons in Ne (Z = 10)
Explanation

Fe²⁺: [Ar]3d⁶ — has 6 d-electrons. Mg: [Ne]3s² — has 2 s-electrons? No, all s-electrons of Mg: 1s²2s²3s² = 6 s-electrons ✓. Cl p-electrons: 2p⁶ + 3p⁵ = 11 p-electrons ≠ 6. Fe: [Ar]3d⁶4s² — has 6 d-electrons ✓. Ne: 2p⁶ = 6 p-electrons ✓. So Cl (11 p-electrons) ≠ 6.

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