Answer
$Al$ is oxidized and $Sn^{2+}$ is reduced.
Work Step by Step
1. Rewrite the equation to show the ions and the atoms:
$2Al(s) + 3Sn^{2+}(g) --\gt 2Al^{3+}(s) + 3Sn(s)$
2. Analyze what happens to each atom/ion during the reaction.
During this process, These are the charge increases/decreases:
$Al^0 --\gt Al^{3+}$: The increase in charge indicates that $Al$ is oxidized.
$Sn^{3+} --\gt Sn^0$: The decrease in charge indicates that $Sn^{2+}$ is reduced.
