oxidation numbers

what do oxidation numbers tell us?

how electrons are lost or gained in a reaction

if an atom has lost electrons will it have a positive or negative oxidation number?

it will have a positive oxidation number

if an atom has gained electrons will it have a positive or negative oxidation number?

it will have a negative oxidation number

when reacted, what is the oxidation number of uncombined elements/pure elements?

0

what is the oxidation state for group 1 metals?

always +1

what is the oxidation number for group 2 metals?

+2

what is always the oxidation number for oxygen?

-2

when can oxygen have an oxidation number of -1?

in peroxides e.g hydrogen peroxide

when reacted with fluorine what is oxygen’s oxidation number?

+2 as fluorine is electronegative enough to remove electrons from oxygen

when reacted, what is always fluorines oxidation number and why?

-1 as it is the most electronegative element so no other element can remove an electron from it

when reacted, what is the oxidation number of halogens?

-1

when can halogens have a positive oxidation number?

if they react with fluorine or oxygen

when reacted, what is hydrogens oxidation number?

+1

when is hydrogens oxidation number -1?

in metal hydrides

what is the oxidation number of aluminium when it reacts?

+3