Final answer:
Aluminum (Al) is oxidized as it goes from an oxidation state of 0 to +3, losing electrons. Bromine (Br2) is reduced since each atom gains electrons, going from an oxidation state of 0 to -1. Oxidation involves losing electrons, while reduction involves gaining electrons.
Step-by-step explanation:
Understanding Redox Reactions
In the chemical reaction 2Al(s) + 3Br2(g) → 2AlBr3(s), we identify what is being oxidized and what is being reduced by determining the change in oxidation states of the reactants going to the products.
Aluminum (Al) starts in its elemental form, so its oxidation state is 0. In the product AlBr3, aluminum is part of a compound and exhibits an oxidation state of +3. Since aluminum goes from 0 to +3, it loses electrons and is therefore oxidized.
Bromine (Br2) starts as a diatomic molecule with an oxidation state of 0. In AlBr3, each bromine has an oxidation state of -1. Bromine gains electrons when it goes from 0 to -1, which means it is reduced.
Oxidation is generally defined as the loss of electrons or an increase in oxidation state by a molecule, atom, or ion. Conversely, reduction is the gain of electrons or a decrease in oxidation state.