Magnesium with atomic number 12 attains the stable electronic configuration of the nearest noble gas :

The correct option is A Neon
Magnesium with atomic number 12 and electronic configuration 2(K), 8(L), 2(M). Therefore, it has two electrons in its valence shell. It donates two electrons from its M shell to attain the stable electronic configuration of the nearest noble gas neon. Thus, the magnesium ion has two positive charges.