redox I Flashcards
what is the oxidation number of uncombined elements/diatomic molecules?
0
what is an oxidation number?
the number of electrons an atom has donated/accepted to form an ion
what is the oxidation number of a monatomic ion?
its charge e.g. Na+ has an oxidation number of +1
what is an oxidising agent?
accept electrons and become reduced
what is a reducing agent?
they donate electrons and become oxidised
what is oxidation?
loss of electrons, molecule becomes positive
what is reduction?
gain of electrons, molecule becomes negative
what is a disproportionation reaction?
when an element in a single species is simultaneously oxidised and reduced
what is the oxidation state of hydrogen?
+1 EXCEPT in metal hydrides where its -1
what is the oxidation state of oxygen?
-2 EXCEPT in peroxides where it is -1
what is the oxidation state of aluminium?
always +3
what is the oxidation state of fluorine?
always -1
what is the oxidation state of chlorine?
-1 EXCEPT if in a compound with oxygen or fluorine where it would be positive
what happens to the oxidation number if electrons are lost?
increases by 1 for every lost electron
what happens to the oxidation number if electrons are gained?
decreases by 1 for every gained electron
what usually happens when a non-metal forms a compound?
forms negative ions by gain of electrons
with a decrease in oxidation number
what usually happens when a metal forms a compound?
forms positive ions by loss of electrons with
an increase in oxidation number
why are oxidation numbers useful?
can classify reactions as redox and as disproportionation
what should be balanced first in a half equation?
anything that isn’t water or oxygen gas
