Oxidation Numbers

An WHAT is the charge an atom WHAT to have when found in a WHAT or charged WHAT

An OXIDATION NUMBER is the charge an atom APPEARS to have when found in a NEUTRAL ATOMS or charged POLYATOMIC IONS

Can be used when you have a WHAT where there are no WHAT to determine if oxidation or reduction is occurring

Can be used when you have a MOLECULAR COMPOUND where there are no ION CHARGES to determine if oxidation or reduction is occurring

How do you use a change in the number?

1. If the number DECREASES then WHAT has occurred as electrons are WHAT (more WHAT)

2. If the number INCREASES then WHAT has occurred as electrons are WHAT (less WHAT)

How do you use a change in the number?

1. If the number DECREASES then REDUCTION has occurred as electrons are GAINED (more NEGATIVE)

2. If the number INCREASES then OXIDATION has occurred as electrons are LOST (less NEGATIVE)

Rules for assigning oxidation numbers

1. In a PURE ELEMENT, the oxidation number is WHAT

2. In SIMPLE IONS, the oxidation number is equal to the WHAT

3. In most compounds containing hydrogen, the oxidation number for hydrogen is WHAT (exception is the metal hydrides where the oxidation number is WHAT)

4. In most compounds containing oxygen the oxidation number of oxygen is WHAT (exception is the peroxides where the oxidation number WHAT)

5. The sum of the oxidation numbers of all the atoms in a substance must equal the WHAT of the substance (WHAT for compounds and WHAT for the polyatomic ion)

Rules for assigning oxidation numbers

1. In a PURE ELEMENT, the oxidation number is ZERO

2. In SIMPLE IONS, the oxidation number is equal to the ION CHARGE

3. In most compounds containing hydrogen, the oxidation number for hydrogen is +1 (exception is the metal hydrides where the oxidation number is -1)

4. In most compounds containing oxygen the oxidation number of oxygen is -2 (exception is the peroxides where the oxidation number -1)

5. The sum of the oxidation numbers of all the atoms in a substance must equal the NET CHARGE of the substance (ZERO for compounds and THE CHARGE for the polyatomic ion)

How to find out which is the OA or RA

1. Look at the change in WHAT of an element from the reactant to product

2. A WHAT means there was a WHAT reaction (electron exchange) in that atom

How to find out which is the OA or RA

1. Look at the change in OXIDATION NUMBER of an element from the reactant to product

2. A CHANGE means there was a REDOX reaction (electron exchange) in that atom

How to identify a redox reaction

1. If WHAT changes in oxidation number, it’s not a redox reaction

2. Thus oxidation numbers are useful for WHAT whether a reaction is redox or not

How to identify a redox reaction

1. If NO ATOM changes in oxidation number, it’s not a redox reaction

2. Thus oxidation numbers are useful for IDENTIFYING whether a reaction is redox or not

WHAT reactions are never redox reaction

Double replacement