Answer:
10 atoms
Step-by-step explanation:
The compound given is:
10MgCl₂
In this compound, we have the atoms:
Mg and Cl;
An atom is the smallest indivisible particle of a substance. They are the smallest particle to take part in chemical reactions.
The coefficient and subscript together determines the number of atoms.
Mg - 10 atoms
Cl - 20 atoms