alleryWhich set of elements forms an isoelectronic series (same number of electrons)?
ACu, Ag, Au, Pt
BNa, Mg, Al, Si
CF⁻, Cl⁻, Br⁻, I⁻
DNa⁺, Mg²⁺, Al³⁺, Ne
Answer & Solution
Correct answer: D. Na⁺, Mg²⁺, Al³⁺, Ne
1. An isoelectronic series has species with the same total electron count.
2. Na⁺ has 11 − 1 = 10 electrons.
3. Mg²⁺ has 12 − 2 = 10 electrons.
4. Al³⁺ has 13 − 3 = 10 electrons.
5. Ne is a neutral atom with 10 electrons.
6. All four species in option A share 10 electrons.
7. The other options contain neutral atoms with different electron counts.
_Source: Selina Concise Chemistry ICSE Class 10, Ch 1 'Periodic Table' (aplustopper.com extract)_
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