What is the chemical formula of magnesium chloride?
MgCl\text{MgCl}MgCl
Mg2Cl\text{Mg}_2\text{Cl}Mg2Cl
MgCl2\text{MgCl}_2MgCl2
Mg2Cl2\text{Mg}_2\text{Cl}_2Mg2Cl2