Which ions are isoelectronic with Ar?

Question

S2+

Ca2+

Cl−

Na+

Answer 1

Ca²⁺and Cl^- are isoelectronic with Ar.

Ar has the electron configuration of [Ne]3s²3p⁶

S = [Ne]3s²3p⁴; S²⁺ = [Ne]3s²3p²

Ca = [Ar]4s²; Ca²⁺ = [Ar]

Cl = [Ne]3s²3p⁵_; Cl^- = [Ar]

Na = [Ne]3s¹; Na⁺ = [Ne]