Answer:
D. a magnesium ion
Explanation:
An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.
All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 12 protons than it must have 12 electrons.
In given question there are 12 protons and 10 electrons which means the neutral atom loses 2 of its valance electrons and form ion.
It is magnesium atom because mass of given atom is
Number of proton+ number of electron = 12+12 = 24 amu
and atomic number is 12.
