BONDING CAPACITY OF FLUORINE

Although fluorine has seven valence electrons, only one of them is unpaired, so the fluorine atom can form one bond. The formula of the compound formed between hydrogen and fluorine is HF and its bond structure is as follows  

The electronegativity difference (1.9) between F(4.0) and H(2.1) is very high, therefore the H — F bond is very polar. 

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Here the central fluorine atom would have two bonds. But the fluorine atom on the right has an electron beyond the octet, and this would require an additional orbital beyond the available four. The bonding capacity of fluorine is thus saturated when the F2 molecule is formed. 

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