In a molecule where all atoms are the same element or diatomic homonuclear molecules, the oxidation number of each atom is

In a molecule where all atoms are the same element or diatomic homonuclear molecules, the oxidation number of each atom is

• A. +1
• B. -1
• C. 0
• D. +2

Answer: (C)

Oxidation numbers are a bookkeeping tool that assign electrons based on differences in electronegativity in bonds. In a molecule composed of identical atoms, bonds are formed between atoms with the same electronegativity, so electrons are shared equally and there is no shift of electron density toward one atom. The overall molecule is neutral, so the sum of oxidation numbers must be zero. With all atoms being the same element, the only way to achieve that zero sum for each atom is to assign an oxidation number of zero to every atom. This applies to any elemental form, including diatomic molecules like O2, N2, H2, and polyatomic clusters of the same element, such as O3. Therefore, the oxidation number of each atom is zero.

Oxidation numbers are a bookkeeping tool that assign electrons based on differences in electronegativity in bonds. In a molecule composed of identical atoms, bonds are formed between atoms with the same electronegativity, so electrons are shared equally and there is no shift of electron density toward one atom. The overall molecule is neutral, so the sum of oxidation numbers must be zero. With all atoms being the same element, the only way to achieve that zero sum for each atom is to assign an oxidation number of zero to every atom. This applies to any elemental form, including diatomic molecules like O2, N2, H2, and polyatomic clusters of the same element, such as O3. Therefore, the oxidation number of each atom is zero.