Which of the following cations is isoelectronic with neon?

Question

Quizplus · Accepted Answer

Neon has an electron configuration of 1s2 2s2 2p6. 
Sodium ion loses its one valence electron to become isoelectronic with neon: 1s2 2s2 2p6. 
Magnesium ion loses its two valence electrons to become isoelectronic with neon: 1s2 2s2 2p6. 
Aluminum ion loses its three valence electrons to become isoelectronic with neon: 1s2 2s2 2p6. 
Therefore, all three cations listed - sodium ion, magnesium ion, and aluminum ion - are isoelectronic with neon.

Which of the Following Cations Is Isoelectronic with Neon