When an atom is oxidized, what change occurs to its oxidation number?

• A. Its oxidation number decreases.
• B. Its oxidation number increases.
• C. It gains electrons and its oxidation number decreases.
• D. Its oxidation number remains unchanged.

Answer: (B)

Verified step by step guidance

1. Understand the concept of oxidation in terms of electron transfer: Oxidation involves the loss of electrons by an atom, ion, or molecule.
2. Recall the definition of oxidation number: It is a hypothetical charge assigned to an atom in a compound, representing the number of electrons lost or gained compared to the neutral atom.
3. Recognize that when an atom loses electrons (oxidation), it has fewer electrons than protons, so its oxidation number increases.
4. Contrast this with reduction, where an atom gains electrons and its oxidation number decreases.
5. Conclude that during oxidation, the oxidation number of the atom increases because it loses electrons.