What is the electron configuration for the ion Ca²⁺?

The correct electron configuration for the ion Ca²⁺ is [Ne]. Calcium (Ca) is in group 2 of the periodic table and has an atomic number of 20, meaning that in its neutral state, it has 20 electrons. The electron configuration for neutral calcium is:

1s² 2s² 2p⁶ 3s²

When calcium loses two electrons to form the Ca²⁺ ion, it loses the two electrons from the outermost shell (the 3s subshell). So, the electron configuration for Ca²⁺ becomes:

1s² 2s² 2p⁶, which is equivalent to the noble gas neon [Ne].

This noble gas configuration indicates that Ca²⁺ has a full outer shell, making it more stable. The other listed choices do not match the electron configuration for the Ca²⁺ ion, as they represent configurations for different elements or ions. Thus, identifying the correct answer as [Ne] reflects an understanding of electron configurations and how ionization affects them.