Oxidation Numbers????

Question

how do you find oxidation numbers when you are given an equation etc..i know we're supposed to use the laws but sometimes i get confused. I am trying to find the oxidation number for AgNO3 and Fe(HCO3)2, can someone help ??

Answer 1

Look at the composition of the substance. AgNO3 is made up of Ag+ and NO3- ions, so since Ag+ is a monatomic ion, its charge is its oxidation number, +1. NO3-, two elements N and O, the addition of the oxidation numbers of N and O must equal the charge, -1. Oxygen is usually -2, (very few exceptions and this ion is not one of them), so using this knowledge:

-1 = 3 (oxid. # O) + oxid. # N
-1 = 3 (-2) + x ==> -1 = -6 + x, thus x = +5 for N.

Fe(HCO3)2, HCO3- is the ion, you have two, so Fe is +2.

H is always +1 when combined with non metals, O is -2 as in the previous example.

So: -1 = +1 + 3(-2) + x

-1 = +1 -6 + x, x = +4, which is the oxidation number of C in HCO3-.

Answer 2

You have an oxidation number for each ion, but the molecules have no charges.
Some ions are always the same oxidation number.
O is always -2 because it has 6 valence electrons ( number at the top of each column in the periodic table) it's missing 2 electrons ; it can only contain 8 electrons. That's the rule but there are a few exceptions.
N is +5
Ag is +1
to figure it out always use the ones that don't change oxygen, hydrogen +1 and you can figure out the rest
example:
Fe (HCO3)2= no charges
O is -2 X3 ions X2 molecules = -12
H is +1X2 molecules=+2
C is +4 (4 valence electrons)= +8
the sum of all charges must = 0, if we add 8+2-12 =-2 then Fe= +2 makes sense as Fe is +2 or +3
I hope this helps!

Answer 3

ok well first of all... O always has an oxidation number of -2 and H always has an oxidation number of +1. N is always -3. This is because your hydrogen and then non-metals have the oxidation number that is the same as the number of electrons in the outer level. So for AgNO3, your O is -2 X 3 which is -6. N is -3. so you now have a -9 so Ag has to be +9 to even it out to 0.
For Fe(HCO3)2 your first want to balance HCO3. H is +1x2 so +2. O is -6. and C can probably be a +4 in this case because of where it sits on the periodic table. Now HCO3 i neutral. Fe is always either 0, +1, +2, or +3. In this case, it's 0.

Answer 4

A compound doesn't have an oxidation number, but each element in it does. It normally corresponds to the valency, followed by + for a metal, and - for a non-metal. Of course it's more complicated than that, and the idea extends to covalent substances as well.
In AgNO3, the Ag is +1, the N is +5 and each O is -2.