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How is the oxidation number of an element in a compound defined?
AThe number of bonds its atoms form
BThe number of electrons in its shells
CThe mass its atoms contribute per mole
DThe charge its atoms would have if ionic
Answer & Solution
Correct answer: D. The charge its atoms would have if ionic
1. Some redox changes make covalent products, where no full electron transfer takes place.
2. Oxidation number handles those cases by asking what charge an atom would carry if the compound were ionic.
3. That makes H2 plus Cl2 giving HCl comparable with sodium plus chlorine giving NaCl.
4. Bond counts and electron shell counts are separate ideas and do not define this quantity.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_
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