Answer:
18 electrons.
Explanations:
According to the question, we have that sulphur has 16 electrons and after bonding with magnesium acquired a 2-charge. The sulphur ion S2- shows that sulphur has gained 2electrons to become stable.
Amount of electron S2- have = 16 electron + 2electrons
Amount of electron S2- have = 18 electrons
Hence the number of electrons S2- ion have is 18 electrons.