In $\ce{SO5^{2-}}$, can somebody tell me which orbitals are used to form the pi bonds in this anion. Please tell the hybridization. And the lewis structure.

Well I tried and the answers I got was sp3 & the pi bonds are formed using d orbitals.I just need to know whether I'm correct

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    – Philipp
    Commented Dec 3, 2014 at 21:09

2 Answers 2


The peroxomonosulfate is a hypercoordinated molecule, in which the sulfur appears to exceed Lewis' rule of two, better known as the octet rule. In former times it was believed that d orbitals would contribute to bonding. This is not the case.
Bonding is better represented by

  • three equivalent $\ce{S-O}$ single bonds
  • sulfur having a formal charge of +2
  • these three oxygens having a formal charge of -1
  • one $\ce{S-O}$ single bond that leads to the peroxyl oxygen
  • this oxygen has a formal charge of zero
  • one $\ce{O-O}$ single bond
  • and the terminal oxygen having a formal charge of -1

This bonding picture is much more in accordance with quantum chemical calculations and an NBO analysis on the DF-BP86/def2-SVP level of theory. The involvement of d orbitals is minimal (<1%).
enter image description here

It is noteworthy, that this molecule pretty much has the same bonding around the sulphur as in sulphate. It can therefore similarly be described. Have a look at my rant against hypervalency or the bonding picture of the $\ce{PO4^{3-}}$ anion, which is isoelectronic to sulphate.


Here is already the Lewis structure

Here is already the Lewis structure

  • $\begingroup$ This question violates our Homework policy. While your effort to answer this problem is very much appreciated, it would be better if you vote (or flag) this question to be closed. We are not a homework answering service. $\endgroup$ Commented Dec 4, 2014 at 1:50
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    $\begingroup$ I see, sorry I'm rather new on the website, I just wnted give a little help :x $\endgroup$
    – Babounet
    Commented Dec 4, 2014 at 7:27

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