Explain, in terms of electronegativity difference, why the bond in a molecule of HF is more polar than the bond in a molecule of HI.

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Answer:

Explanation:

Electronegativity is defined as the ability of an element to attract electrons that link it to another element.

The covalent bond (chemical bond between atoms where electrons are shared, forming a molecule. This bond is established between non-metallic elements) between two atoms can be polar or nonpolar.

When two atoms have different electronegativities, the one with the highest electronegativity will attract the electrons towards each other, generating a separation between the positive and negative charges. In this way a polar bond is produced, the polarity of which will be as the electronegativity difference between the bonded atoms is greater.

In this case you know the following electronegativities:

  • H=2.1
  • F=4.0
  • I=2.5

So the electronegativity differences in the HI and HCl compounds are:

  • HF =4.0 - 2.1= 1.9
  • HI = 2.5 - 2.1= 0.4

Both compounds have element H that is part of it, only differing in F and I. Since F has greater electronegativity than I, the difference in electronegativity in compound HF will be greater. Then the HF compound will be more polar.