3.1.7 - Oxidation, reduction and redox equations

loss of electrons

gain of electrons

a reaction where reduction and oxidation happen simultaneously

oxidising agent accepts electrons and gets reduced

reducing agent donates electrons and gets oxidised

oxidation state of an element tells you the total number of electrons it has donated or accepted

oxidation numbers

uncombined elements have oxidation state of 0

elements just bonded to identical atoms have oxidation state of 0

oxidation states of simple monoatomic ions is the same as its charge

e.g. Na1+ has oxidation state +1

overall change on the ion

most electronegative element has a negative oxidation state (equal to its ionic charge)

+1, except when bonded to a metal, metal must have positive oxidation number

-2, except when bonded to F or in peroxides , F must have the negative oxidation number

increase in oxidation number = oxidation

decrease in oxidation number = reduction

assign oxidation states, tells us what is reduced and oxidised

balance the elements with changing oxidation states

add electrons as needed in order to change the oxidation state (charge must balance)

add H2O to balance oxygen

add H+/OH- to balance hydrogen

NH4 +

CO3 2-