Question #2de62

1 Answer
Nov 26, 2016

#Fe_"2"O_"3"# has an iron atom with a charge of 3+, while the #FeO# has a charge of 2+.


Iron #(Fe)# is a multivalent element. Having two different charges, 3+ and 2+. These charges partake in chemical reactions with other elements because these charges are in sync with its electron configuration.

We know that atoms react to become stable.

Having a charge of 3+ means the atom has 3 excess electrons, likewise, a charge of 2+ means it has two extra electrons from being stable.

If iron with a charge of 3+ reacts with oxygen, we would need 3 atoms of oxygen for the compound to be neutrally charged - stable while iron would need 2. Thus, Iron (III) oxide = #Fe_"2"O_"3"#.

If iron with a charge of 2+ reacts with oxygen, we would need 2 atoms of oxygen and iron for the compound to be stable. Thus, Iron (II) oxide = #FeO# (the subscripts were reduced/simplified to 1 and is not shown).

When writing chemical formula for compounds with multivalent elements, we use a bracket with roman numerals to indicate which variant the anion reacted with.
E.g. Lead (IV) oxide = #PbO_"2"# - the subscripts were reduced.

Hope this helps :)