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Electronegativity refers to the ability of an atom to attract electrons when it forms bonds with other atoms. Different elements have different electronegativities, which can affect the properties of the molecules they form.
For example, fluorine is the most electronegative element, meaning it very strongly attracts electrons.
On the other hand, hydrogen has a relatively low electronegativity.
When two atoms with different electronegativities bond, the shared electrons are drawn more towards the atom with the higher electronegativity.
This creates a partial negative charge near the more electronegative atom and a partial positive charge near the less electronegative atom.
This difference in charge distribution within the molecule is a key factor in determining its dipole moment.

Molecular polarity is determined by the distribution of electrical charges across a molecule.
If a molecule has regions with slight positive and negative charges due to the presence of atoms with different electronegativities, it is considered polar.
Polarity influences many properties of a molecule, like its boiling point and solubility in water.
For instance, water \(\text{H}_2\text{O}\) is highly polar because oxygen has a much higher electronegativity than hydrogen.
This results in the oxygen atom carrying a partial negative charge and the hydrogen atoms carrying partial positive charges.
The shape of the molecule also plays a role in determining polarity.
If the polar bonds are arranged symmetrically, the charges may cancel out, making the molecule nonpolar despite having polar bonds.
In our exercise, we determined that molecules like \(\text{H}_2\) and \(\text{O}_2\) are nonpolar because they consist of two identical atoms sharing electrons equally.

The dipole moment of a molecule is a measure of its overall polarity and is determined by both the magnitude of the charges and their separation distance.
The unit of dipole moment is the Debye (D). To estimate the dipole moment, you need to know:

• The electronegativity difference between the atoms involved.
• The distance between the charges, which correlates with the bond length.

In our exercise, \(\text{HF}\) has a significant dipole moment because of the large electronegativity difference between hydrogen and fluorine and the bond length between these atoms.
Similarly, \(\text{HBr}\) also has a dipole moment but it is smaller because bromine is less electronegative compared to fluorine.
No dipole moment is present in \(\text{H}_2\) and \(\text{O}_2\) because they consist of identical atoms that share electrons equally.
This comprehensive understanding helps you predict that \(\text{HF}\) will have the greatest dipole moment among the given options.