The answer is D) a neutron.
When we say an atom's mass is, like 5 atomic mass units actually we are saying that the total number of the neutrons and protons in its nucleus is 5.
The mass of a neutron and a proton is each one atomic mass unit.
Mass of a neutron is approximately 1 atomic mass unit.
It is called a polyatomic ion.
Hope this helps!!!
C is the answer hope this helps
Magnesium in hydrochloric acid forms H2 (hydrogen) gas according to the balanced chemical equation:
Mg + 2HCl→H2 + MgCl2
