The oxidation number of a monatomic ion is the charge of the ion.

For example, in NaCl, the oxidation number of Na is +1, while the oxidation of Cl is -1. The sum of all the oxidation numbers of the atoms in a neutral compound is 0.For example, the oxidation number of C, Ne, O 3, N 2, and Cl 2 is 0. The oxidation number of a free element or neutral molecule is 0.The latter form is used to indicate oxidation state. For example, write +1 and -3 rather than 1+ and 3. Write the oxidation number with the sign of the charge followed by its value.For example, in HCl, the H is H +, but in NaH, the H is H –. Some atoms may be either the cation or anion, depending on the other elements in the compound. The cation is the more electropositive atom or ion, while the anion is the more electronegative atom or ion. Write the cation first in a chemical formula, followed by the anion.Here is a list of oxidation number rules: Various texts contain different numbers of rules and may change their order. This is a list of rules for assigning oxidation numbers, with examples showing the numbers for elements, compounds, and ions. Because they track the number of electrons lost or gained, oxidation numbers are a sort of shorthand for balancing charge in chemical formulas. In other words, the oxidation number gives the degree of oxidation (loss of electrons) or reduction (gain of electrons) of the atom in a compound. The oxidation number is the positive or negative number of an atom that indicates the electrical charge the atom has if its compound consists of ions. Otherwise, the total charge is ionic charge. The oxidation number of an element or neutral compound is zero. This entry was posted on Februby Anne Helmenstine (updated on July 13, 2021)

Assigning oxidation numbers