Answer:
Mg (s) is the oxidized substance and [tex]Cl_{2}[/tex] (g) is the reduced substance
Explanation:
If oxidation number of a substance increases then that substance is being oxidized. This is due to release of electron from that substance.
If oxidation number of a substance decreases then that substance is being reduced. This is due to consumption of electrons by that substance.
Element oxidation number
Mg(s) 0
[tex]Cl_{2}[/tex] 0 (Cl)
[tex]Mg^{2+}[/tex] +2 (Mg)
[tex]Cl^{-}[/tex] -1 (Cl)
So oxidation number of Mg increases by +2 which occurs due to release of two electrons from Mg (s). Hence Mg (s) is being oxidized.
And oxidation number of Cl decreases by -1 which occurs due to consumption of one electron by [tex]Cl_{2}[/tex] (g). Hence [tex]Cl_{2}[/tex] (g) is being reduced.