Final answer:
When a compound is oxidized, the oxidation number of the element being oxidized is increased. This is due to the loss of electrons which causes an increase in the oxidation number. The correct option is 1.
Step-by-step explanation:
When a compound is oxidized, the oxidation number of the element being oxidized is increased. This is because oxidation involves the loss of electrons from the element, and a loss of electrons leads to an increase in the oxidation number.
To maintain charge balance in the reaction, the increase in the oxidation number for the atom that is oxidized must be balanced by an equivalent decrease in the oxidation number of the atom that is reduced. This is essential in order to have a balanced redox equation.
For instance, in the oxidation of carbon, the carbon atom's oxidation number increases. Conversely, in the reduction of iron, the iron atom's oxidation number decreases. Such changes are crucial in identifying the substance being oxidized and the one being reduced in redox reactions.
Rules for assigning oxidation numbers are:
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- The oxidation number of an atom in an elemental substance is zero.
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- The oxidation number of a monatomic ion is equal to the ion's charge.
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- For hydrogen, the oxidation number is +1 when combined with nonmetals, and -1 when combined with metals.
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- Oxygen usually has an oxidation number of -2 in compounds, except in peroxides or superoxides.
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- Halogens such as fluorine have an oxidation number of -1, but this can vary when in compounds with oxygen or other halogens.