What concept describes the number of electrons an atom can give up, with positive valence numbers donating and negative numbers receiving?

• A. Valence
• B. Electron affinity
• C. Oxidation state
• D. Ionization energy

Answer: (A)

Oxidation state (oxidation number) is the concept described here. It’s a bookkeeping way to say how many electrons an atom would lose or gain in a reaction or compound. When an atom has a positive oxidation state, it effectively has given up electrons; when it has a negative oxidation state, it has gained electrons. The magnitude tells you how many electrons are involved. For example, in common salts, sodium has an oxidation state of +1 (it’s imagined as losing one electron) and chlorine has -1 (gaining one electron).

Valence is related but broader; it refers to the bonding capacity or how many electrons an atom can share or transfer in general, which can vary by context. Oxidation state is a precise, formal way to express electron transfer in bonds, which is why it’s the best fit for this description.