[jsmith613]

What is the formula for sodium chlorate (VII)

[Schrödinger]

http://lmgtfy.com/?q=sodium+chlorate+(VII)

[jsmith613]

http://lmgtfy.com/?q=sodium+chlorate+(VII)

I found the answer NaClO4. They said that the element with a variable oxidation state adopts the charge in the brackets BUT i thought chlorine did not have a variable valency and than oxygen did?
So why in this case is it chlroine with the variable valency

[Schrödinger]

Chlorine is attached to an atom,oxygen, that is more electronegative than itself... Hence the usual negative oxidation state is not found here. Cl's oxidation state is positive here.

Moreover, Cl has vacant d-orbitals and O doesn't. Hence, Cl can exhibit variable oxidation states and O cannot.

[rabolisk]

Rules for oxidation states

1. Free atoms (0 charge) are 0
2. The overall charge of a compound equals the sum of oxidation states of its constituent elements.
3. Fluorine is -1 if it is bonded to anything other than itself, always.
4. Hydrogen is always +1 or -1 if it is bonded to anything other than itself.
5. Oxygen is almost always -2 if it is bonded to anything other than itself. Peroxides and superoxides are exceptions.
6. Group I elements are +1, and Group II elements are +2.

You can see that there is no rule for chlorine in a compound. But rules 2, 5, and 6 can be used to figure out the oxidation state of chlorine.