Final answer:
The correct electron configuration for Fe2+ ions is B) [Ar]3d6, since the 4s electrons are removed first when iron forms a 2+ ion.
Step-by-step explanation:
The question asks which electron configuration represents Fe2+ ions. The atomic number of iron (Fe) is 26, which normally has a configuration of [Ar] 4s2 3d6. However, when Fe loses two electrons to form Fe2+, the electrons are removed from the 4s orbital first, giving us [Ar]3d6. Therefore, the correct electron configuration for Fe2+ is option B) [Ar]3d6.