* Oxidation: Loss of electrons.
* Reduction: Gain of electrons.
Let's look at the changes in oxidation states:
* Sodium (Na): Starts as elemental sodium with an oxidation state of 0. It ends up as sodium ion (Na+) in NaOH, with an oxidation state of +1. This means sodium *lost* an electron, so it was oxidized.
* Hydrogen (H): Starts as +1 in water (H₂O) and ends up as 0 in hydrogen gas (H₂). This means hydrogen *gained* an electron, so it was reduced.
Therefore, while the overall reaction is a redox reaction (both oxidation and reduction occur), the specific element that is reduced is sodium.
