Which of the following ions is isoelectronic with the noble gas neon?

Name: Which of the following ions is isoelectronic with the noble gas neon?
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Question

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Isoelectronic species have the same number of electrons. 
Neon has 10 electrons. 
F- has 10 electrons (1 gained electron to have a total of 10)
Na+ has 10 electrons (1 lost electron to have a total of 10)
Mg2+ has 10 electrons (2 lost electrons to have a total of 10)
Al3+ has 10 electrons (3 lost electrons to have a total of 10)

Which of the Following Ions Is Isoelectronic with the Noble