Redox - Oxidation states rules

if oxidation number increases…

oxidation occurs

if oxidation number decreases…

reduction occurs

element in free state

always 0

monatomic ion

equals its charge

complex ions

oxidation states add up to charge

flourine

always -1

except as an element = 0

oxygen

usually -2

except as an element = 0

in peroxides annd with flourine = -1

hydrogen

usually +1

except as an element = 0

or in metal hydrides = -1

halogens

usually -1

except as an element = 0

or when bonded to more electronegative elements

Group 1 metals

Always +1

Group 2 metals

Always +2

Transition metals

Can vary