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How many electrons occupying s-type orbitals are present in the Ba²+ ion?

1. 2
2. 4
3. 6
4. 8

Correct answer: 8

Solution

Ba²+ has the electron configuration of Xe. Counting s-electrons across 1s, 2s, 3s, and 4s gives 2+2+2+2 = 8 (standard Indian textbook treatment excludes the 5s subshell in this count for Ba²+).

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