chemistry help

[thubby]

oh great minds of the playground, i beseech thee, aid my poor stupid brain. *starts chanting and dancing*

anywho.
i need to figure out the oxidation number of N in K3Fe(CN)6

i know k is +1 because it's an alkali metal. after that im at a loss

[Don Julio Anejo]

Fe can be 2+ or 3+, in this case it's 3+ since cyanide is -1 and 6 cyanides are -6.

N is usually -3 unless paired bound to something very electronegative like fluorine or oxygen. In this case it's bound to carbon, which isn't very electronegative.

This makes nitrogen -3 and carbon +2.

[Eldan]

Edit: What the person above me said.

[thubby]

how do you know cyanide is -1?

[Science Officer]

how do you know cyanide is -1?

isn't it sometimes listed as a poly-atomic ion? also HCN is a molecule, so...

EDIT: also, in this case, it wouldn't really work if it was -2 charge or greater (in magnitude).

[Tavar]

Cyanide is one of the common polyatomic ions. There's probably a list somewhere in your book of the common ones that they want you to memorize, and this is one of them.

[Eldan]

Another way to remember it is that there's a triple bond between Carbon and Nitrogen. That leaves one free "space" on the carbon, so -1.