The equation presented above is that of uranium reacting with fluorine forming uranium fluoride.
The chemical reaction can be balanced by carefully studying the equation and balancing the number of atoms of each of the element in both sides of the chemical reaction. That is,
<em> U(s) + 3F₂(g) --> UF₆(g)</em>
The particular reaction that represents the oxidation of Mg metal would be the following:
Mg => Mg+2 + 2e-
This is the half reaction of the oxidation of the magnesium metal, another charged species would need to receive it to become reduced or gain the 2 electrons lost.