Which of the following is an isoelectronic series? F-, Cl-, Br-, I - O2-, F-, Ne, Na + S, Cl, Ar, K Si2-, P2-, S2-, Cl2-

(b) O²⁻, F⁻, Ne, Na⁺

Explanation:

An isoelectronic series is a sequence of atoms/ions with the same electron configuration.

(a) F⁻, Cl⁻, Br⁻, I⁻

F⁻: [He] 2s²2p⁵

Cl⁻: [Ne] 3s²3p⁵

Br⁻: [Ar] 4s²4p⁵

I⁻: [Kr] 5s²5p⁵

The ions all have different electron configurations. Not isoelectronic.

(b) O²⁻, F⁻, Ne, Na⁺

O²⁻: [Ne]

F⁻ : [Ne]

Ne: [Ne]

Na⁺: [Ne]

The species all have the same electron configuration. Isoelectronic.

(c) S, Cl, Ar, K

S: [Ne] 3s²3p⁴

Cl: [Ne] 3s²3p⁵

Ar: [Ar]

K: [Ar] 4s

The atoms all have different electron configurations. Not isoelectronic.

(d) Si²⁻, P²⁻, S²⁻-, Cl²⁻

Si²⁻: [Ne] 3s²3p⁴

P²⁻: [Ne] 3s²3p⁵

S²⁻: [Ar]

Cl²⁻: [Ar] 4s

The ions all have different electron configurations. Not isoelectronic.