What are the oxidation numbers of Fe, N and O in the compound Fe(NO3)3?

1 Answer
Nov 1, 2015

Answer:

Oxidation number is the charge left on the central atom, when all the bonding electrons are removed with the charge devolving to the most electronegative atom.

Explanation:

Clearly the oxidation number of the iron centre is #III+#, as 3 nitrate ions are bound to this centre:

#Fe(NO_3)_3rarrFe^(3+) + 3NO_3^-#;

Now to determine the oxidation state of nitrogen, we know that #3xxON_(O)+ON_N = -1#. Why? Because the sum of the oxidation numbers must equal the charge on the ion. #ON_(O)# is normally #-II#, and it is here, so #3xx(-2)+ON_N = -1#. Oxidation number of nitrogen is #V+#.

I would have got the same result had I used the definition of oxidation state, i.e. #NO_3^(-) rarr N^(5+) + 3xxO^(2-)#.

What are the oxidation states of the metal in #FeCl_4^-#, #MnO_4^-#, and #Cr_2O_7^(2-)#?