If the oxidation number of phosphorus changes from -3 to 0, what happened to phosphorus?

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Multiple Choice

If the oxidation number of phosphorus changes from -3 to 0, what happened to phosphorus?

Oxidation numbers reflect electron transfer: an increase means oxidation (loss of electrons), a decrease means reduction (gain of electrons). If phosphorus changes from -3 to 0, its oxidation state has risen by 3, so it must have shed three electrons. That is oxidation, and the element becomes oxidized in the process. For context, a phosphide ion carries a -3 state, while elemental phosphorus is at oxidation state 0, so moving from -3 to 0 corresponds to losing three electrons. The other ideas would require gaining electrons (which would lower the oxidation state) or mixing oxidation with reduction, which doesn’t match the observed increase in oxidation state.

Oxidation numbers reflect electron transfer: an increase means oxidation (loss of electrons), a decrease means reduction (gain of electrons). If phosphorus changes from -3 to 0, its oxidation state has risen by 3, so it must have shed three electrons. That is oxidation, and the element becomes oxidized in the process. For context, a phosphide ion carries a -3 state, while elemental phosphorus is at oxidation state 0, so moving from -3 to 0 corresponds to losing three electrons. The other ideas would require gaining electrons (which would lower the oxidation state) or mixing oxidation with reduction, which doesn’t match the observed increase in oxidation state.

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