Answer:
Mg + 2Cl ----> MgCl2
Step-by-step explanation:
In writing a chemical reaction equation, it is a rule that the number of atoms of each element on the right hand side must be equal to the number of atoms of each element on the left hand side.
If this condition is fulfilled, the reaction equation is said to be balanced.
In this case, there are two chlorine atoms and one magnesium atom on both sides of the reaction equation hence the equation is balanced.