Changing Oxidation Numbers

How do oxidation numbers go up or down?

As electrons are lost or gained.

How will the oxidation number increase?

By 1 for each electrons lost

How will the oxidation number decrease?

By 1 for each electron gained.

What happens when metals form compounds?

They generally donate electrons to form positive ions and is accompanied by an increase in oxidation number

What happens when non- metals form compounds?

They generally gain electrons and form negative ions and is accompanied by a decrease in oxidation number

What happens in redox reactions?

Some oxidation numbers will change as something will lose electrons and end up with an increased oxidation number and something will gain electrons and end up with a decreased oxidation number.

How can you work out which substance in a reaction acts as a reducing or oxidising agent?

Once you've identified how the oxidation numbers of elements and ions change in a reaction.

What should you do when asked about oxidation and reduction?

Work out the oxidation numbers of each atom or ion to see exactly how the electrons are moving around.

How can metals have positive oxidation numbers?

When metals form compounds and donate electrons to form positive ions.

How can non-metals have negative oxidation numbers?

When non-metals form compounds and gain electrons.