Couple of chem questions I don't understand

[Starlight]

Hey I just have a couple of chem questions (i'm actually doing fundamentals of chem at uni but it is essentially vce level so i thought i'd post here)

1. What does it mean when Iron has two different oxidaiton states (as indicated by those roman numeral thingies when it reacts with another element) Apparently they form compounds mainly in the 2+ 3+ oxidation states, what does this mean???

2. How do you write the formula for 'sodium peroxide?' How come its Na202?

What does 'peroxide' mean?

[ggxoxo]

A peroxide is a compound that has a peroxide/peroxo group (i.e. O-O group) e.g. Hydrogen peroxide, H2O2

[SenriAkane]

Hey I just have a couple of chem questions (i'm actually doing fundamentals of chem at uni but it is essentially vce level so i thought i'd post here)

1. What does it mean when Iron has two different oxidaiton states (as indicated by those roman numeral thingies when it reacts with another element) Apparently they form compounds mainly in the 2+ 3+ oxidation states, what does this mean???

Iron can lose 2 electrons from 4s orbital to form Iron (II). Leaving 3d6 as the outer shell, as 3d6 has a orbital configuration of |2+1+1+1+1| it is relatively unstable as electron-electron repulsion occurs where 2 electrons are contained in the same space.

Hence 3+ ion can be formed by removing 1 electrons from 3d orbital so the 5 electrons left (3d5) over can each occupy an orbital itself (1+1+1+1+1) leading to a lower energy level compared to 3d6

[Starlight]

Thanks guys

[pi]

2. How do you write the formula for 'sodium peroxide?' How come its Na202?

That's correct, Na2O2. I think the structure is Na-O-O-Na, but I'm not sure as this fits into a lattice...