The Bond in a Hydrogen Halide

and HI are called hydrogen halides. A halogen has only one unpaired valence electron (Table 1.2), so it forms only one covalent bond. 

Therefore, we will assume that the hydrogen-halogen bond is formed by the overlap of an sp orbital of the halogen with the. y orbital of hydrogen. 

In the case of fluorine, the sp orbital used in bond formation belongs to the second shell of electrons. In chlorine, the sp orbital belongs to the third shell. Because the 

There is greater electron density in the region of overlap of the s orbital of hydrogen with a 2sp orbital than in the region of overlap of the s orbital of hydrogen with a 3sp orbital, which is greater than in the 

The hydrogen-halogen bond becomes longer and weaker as the size of the halogen increases. 

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