[cliverlong]

Hello,

I have seen that chlorine can achieve 5 oxidation states

-1, +1, +3, +5, +7

The positive oxidation states are for the following chlorates

ClO^- (+1), ClO₂^- (+3), ClO₃^- (+5),  ClO₄^- (+7)

I'm trying to understand where the electrons “go” when these anions are formed

The electronic configuration of the chlorine atom is 2.8.7

Now if I think of promoting electrons in the chlorine atom from the 3p orbitals into 4s and 4p I can create the correct number of unpaired electrons to account for the formulae. But is the following correct?

ClO^- (+1). Promote one 3s electron to 4s. Creates three unpaired electrons, two in 3p one in 4s. An oxygen atom bonds with two 3p electrons leaving an unpaired 4s electron. One further electron goes into the 4s orbital making the charge -1

Similarly

ClO₂^- (+3). two 3p electrons promoted to 4s and 4p (a hybridized 4sp¹ ?). Two oxygen atoms bond with 4 unpaired electrons in three lots 3p and one 4sp¹. Extra electron in 4sp¹ to give negative charge

ClO₃^- (+5) One 3s electron and two 3p electrons promoted to 4s and 4p (a hybridized 4sp² ?). Three oxygen atoms bond with 6 unpaired electrons in one 3s three lots 3p and two 4sp². Extra electron in 4sp² to give negative charge.


Thanks

Clive

[enahs]

They go in the bonds between the atoms. Oxidation state is just a book keeping method. It does not really represent anything physical.

[cliverlong]

Oxidation state is just a book keeping method. It does not really represent anything physical.

Ok, I get that now

I'm trying to understand where the electrons “go” when these anions are formed

They go in the bonds between the atoms.

I don't understand what you mean. Is it possible to explain which orbitals (atomic or hybrid) the bonding electrons occupy - and show from which "base" orbitals in the chlorine atom the electrons originate?

Thanks

Clive

[enahs]

Is it possible to explain which orbitals (atomic or hybrid) the bonding electrons occupy - and show from which "base" orbitals in the chlorine atom the electrons originate?

Yes, example:
AO₄^n-, such as phosphate (PO₄^3-), sulfate (SO₄^2-) and perchlorate (ClO₄^-) are isostructural and isoelectronic. The central atom (A) is tetrahedrally surrounded by 4 oxygen atoms, and the octet is achieved by when single bonds are exclusively used. There can however be additional π bonding that increases the electron density on the central atom. This π bonding will make use of the empty d orbitals on the central atom through dπ-pπ overlap. This requires a rehybridization of of terminal oxygen atoms from sp³ (A-O groups) to sp² (A=O groups). The terminal oxygen atoms are said to be π donors and the central atom is referred to as a π acceptor. This is most evident in the case of the perchlorate because Cl is the most electronegative in the given examples. For elements of the row 3 and below, dπ-pπ bonding is prominent because of the presence of valence-level d-orbitals.