Question

Fe(NO3)2 not sure how to get the oxidation numbers of all elements

Answer 1

Is there a specific part that is giving you trouble? Or just completely uncertain where to begin?

Answer 2

yes im confused with poly atomic ions part in the compound Fe(NO3)2 not sure if i multiply ()O3)times2 which is -6 , what is n and fe not sure how else to explain

Answer 3

So, Fe(NO3)2
The NO3 part is a polyatomic ion with total charge -1. (this is because Fe has a +2 charge and two NO3's with a -1 charge will balance out to 0).

Most often we just make the assumption that Oxygen has a -2 oxidation number because it is very electronegative. So to find N, we just need an oxidation number that balances out with 3(-2) to get -1 (the ttotal charge of the ion)

Answer 4

So your suspicion to multiply -2 by 3 is correct. Nitrogen will take the oxidation number that adds with the -6 to get -1.

Answer 5

so correct me if im wrong ,Fe is +5

Answer 6

The nitrogen's oxidation number is the one that adds with -6 to get -1, not iron.

The iron takes the same oxidation number as its charge in the atom.

Answer 7

Fe (NO3)2
if we reverse cross rule with the subscripts to find charges...
Fe 2+ NO3 1-

Answer 8

still not clicking chem is giving me trouble could i see you work it out maybe it would click then

Answer 9

Aye. I will start from the beginning.
Fe (NO3)2
Singular ions have the oxidation number equal to their charge. Iron is one such lonesome ion.
Fe charge 2+ || NO3 charge 1-
So you can plainly see where Iron will get the oxidation number of +2.

For the Polyatomic Ion, the oxidation numbers will sum to -1, the total charge of the Polyatomic Ion.
Oxygen is a strongly electronegative atom, so we can assume in this case it has its usual oxidation number of -2.
Thus, Nitrogen has to balance with Oxygen to obtain the total of -1.
-2(3) + N = -1
-6 + N = -1
Thus we just solve to obtain Nitrogen's oxidation number.

Answer 10

ok so Fe has a +2 N has a + 5 , O has -6

Answer 11

Almost! Oxygen alone just has -2. The -6 comes from -2*3 which is resulting from there being three Oxygens in the polyatomic ion. The individual Oxygen has -2, three together have -6.

Answer 12

so what is Fe sorry that im being difficult

Answer 13

The other two you had were okay.
Fe is indeed +2.

And it is no trouble, as long as I am able to help. :)

Answer 14

i figured it out , this is what i wasnt doing: once i egot the individual elements for instance nitrogen is +5, O is -6 then i multiply by the 3 outside the (NO3 )3

Answer 15

Oo, Dumb mixup on my post I made and deleted.

In a sense, the oxidation number literally is telling us how electrons are changing hands between atoms assuming they do so completely. Notice that this is an ionic bond, so the metal donates some electrons to the anion. How many would it give? Well, it gave two away, leaving it with a charge of +2 as each NO3 anion gains one electron becoming -1 and -1.

Inside the polyatomic anion is covalent bonds, so they are technically shared. But our oxidation number is essentially how it would go if they entirely transferredt. Oxygen looves electrons, so it steals them away from the weaker Nitrogen. There are three oxygens coming after these electrons too, so they all take away their share of -2. Nitrogen has 5 electrons to give, and it also takes one electron from the Iron earlier. It is left with a charge +5.

Also is it a 3 on the outside? Fe(NO3)3 or Fe(NO3)2 ?

Answer 16

The original question said Fe(NO3)2 but Fe(NO3)3 leaves iron with a different charge.

Answer 17

yes! i may have explained it wrong, but her is the problem: 3 Fe(NO3)2(ag)+2Al(s)-->3Fe(s)+2Al(NO3)3(ag)

Answer 18

ohhh got it, it's a coefficient of 3 on Fe(NO3)2 not subscript
what we did was all good then.

we wouldn't multiply the coefficient onto it because this is individual atoms we are referring to. N itself has +5. More than one together may have something like +15 for 3 N's but we wanted the precise oxidation number of one element.

the only purpose of considering multiple atoms of the element would be when we are considering the whole molecule or polyatomic ion, they all add up together. But the basis is still what one atom has for its oxidation number..

Answer 19

Thanks only if i could explain it as well as you i may be feel better going to class.

Answer 20

glad to help!
and it does come down to practice with these sometimes. chemistry is just full of information to commit to memory, i don't think I could ever get by without lots of notes and practice problems. :p

Answer 21

yea your correct notes,etc