Final answer:
To determine what is being oxidized and reduced in a redox reaction, we need to look at the charges of the atoms involved and see if they increase or decrease. By assigning oxidation numbers to the atoms, we can identify the species being oxidized and reduced.
Step-by-step explanation:
To determine what is being oxidized and reduced in a redox reaction, we need to look at the charges of the atoms involved and see if they increase or decrease. If the charge increases, the atom is being oxidized, and if the charge decreases, the atom is being reduced. By assigning oxidation numbers to the atoms, we can identify the species being oxidized and reduced. For example, in the reaction Sr + SO3 -> SrSO3, the oxidation number of sulfur increases from +4 to +6, indicating that sulfur is being oxidized, while the oxidation number of strontium remains the same, indicating that it is not being oxidized or reduced.