To balance the chemical equation \( \text{Mg} + \text{F}_2 \rightarrow \text{MgF}_2 \), we need to ensure that the number of each type of atom is the same on both sides of the equation.
On the left side:
- We have 1 magnesium (Mg)
- We have 2 fluorine (F) from \( \text{F}_2 \)
On the right side:
- We have 1 magnesium in \( \text{MgF}_2 \)
- We have 2 fluorine in \( \text{MgF}_2 \)
Since there is already 1 Mg and 2 F on both sides, the balanced equation is:
1 Mg + 1 F2 → 1 MgF2
Thus, the coefficients are 1:1:1.
So the correct answer is: a 1:1:1.