oxidation number
oxidation state

The oxidation number of the most common chalcogen compounds is 2.

However, oxidation number is used in coordination chemistry with a slightly different meaning.

The oxidation number on all atoms in such a reaction remains unchanged.

So why assume there is electron transfer, or oxidation number?

The oxidation number of an element is equal to its combining power with oxygen.

There are a number of rules for calculating oxidation numbers.

How would one go about changing the oxidation number of copper?

He said that -1 is not its charge, but a fictitious oxidation number.

A given compound may have more than one oxidation number depending upon what it is reacting with.

The properties of the atoms involved can be understood using concepts such as oxidation number.