Oxidation numbers?

Question

How do you know when a molecule a neutral in order to calculate its oxidation number?

Answer 1

OK lets say you have a moluecule HSO4 (hydrogen sulfate)

And you need to find the oxidation number for S
1)If you dont know the oxidation numbers already ill show you
Alkilie(forgive my spelling) metals = +1(oxidation number)
Alkilie earth metals = +2

*The transitions metals are a bit different but we do not need to know them

starting with the element B(boron)and its cloumn=+3
C and its column= +or - 4
N " " = -3
O" " = -2
F" " =-1

*the noble gases dont have oxidation numbers because they are already stable and thay dont want to change their state.

Now you are given HSO4

And H(hydrogen) = +1
And O(oxygen) = -2x4=-8(because you have 4 oxygens)
S=?

You can combine the +1 and -8 to get S which is -7

So the oxidation number for S is -7
*not all cases will an element have the same oxidation number

ex. H2SO4
S is different

Answer 2

a molecule neutral when it doesn't have sign " - " or " +" at the top right of the molecule ( other way, it have the total oxidation # = 0 ). when it have either sign, it is ion ( maybe polyatomic ion or metal or non-metal ion )

refer to the unchangeable rule of oxidation # of some element in your text book for further infomation ( e.g Halogen is always equal to -1, alkaline always equals +1, Oxygen always equal -2 expect for peroxide equal to -1 etc....)

Answer 3

All molecules are neutral by their nature. Only the poly-atomic ions have charge on them. Learn to recognize the poly-atomic ions an you will be able to determine if they are charged. See your text-book for a list of the common poly-atomic ions.