In this question, we have to balance the equation and also tell the physical state of matter of each compound, the balanced reaction will be written as it follows:
Mg + I2:-> MgI2
In this way, the reaction is already balanced, and the physical states are:
Mg (s) + I2 (s) -> MgI2 (s)
This is how the reaction will behave in terms of balancing and also the natural physical states of each compound