Question

Explain why fluorine forms only one oxoacid, HOF.

Answer 1

Hint: The formation of an oxoacid relates to the concept of oxidation state represented by the element. It also depends upon the size and the electronegativity of the element.

Complete step by step answer:

• Firstly, fluorine belongs to the halogen group. It’s atomic no. is 9, and the electronic configuration 1s$^{2}$2s$^{2}$2p$^{5}$. It is the smallest element in the halogen group.
• Secondly, we can see from the electronic configuration that there is absence of d-orbitals. *
• It represents -1 oxidation state in general.
• Fluorine has very high electronegativity.
• To calculate the oxidation state of fluorine in HOF, H has +1 charge, O has -2 charge, let the charge of fluorine be x. Therefore, HOF = +1-2+(x) = 0, we considered overall charge as it is a neutral compound, here we can see the value of x is +1. So, now we know the oxidation state of fluorine in HOF is +1.
• Due to the absence of d- orbitals, fluorine doesn’t form the oxoacids having higher oxidation states such as +3, +5, or +7.
  So, the +1 oxidation state is shown by fluorine only with the element oxygen.
  Thus, it forms only one oxoacid, HOF.

Note: Don’t get confused in between the properties of fluorine. It shows +1 oxidation state in HOF, as it is surrounded by the oxygen atom. To form the other oxoacids, the higher oxidation state is required.