The molecule hydrogen fluoride (HF) contains a polar bond H – F, where fluorine is more electronegative than hydrogen. Which is the appropriate representation of the H – F bond?
The correct answer and explanation is:
Correct Answer:
δ⁺H — Fδ⁻
Explanation:
The hydrogen fluoride (HF) molecule contains a single covalent bond between a hydrogen atom and a fluorine atom. However, this bond is not shared equally. The unequal sharing of electrons is due to a significant difference in electronegativity between hydrogen and fluorine.
Electronegativity is the ability of an atom to attract bonding electrons toward itself. Fluorine is the most electronegative element on the periodic table, while hydrogen has a much lower electronegativity. As a result, the bonding electrons in the H—F bond are pulled more strongly toward the fluorine atom.
This unequal sharing leads to the formation of partial charges on the atoms. Fluorine develops a partial negative charge (δ⁻) because it attracts the electrons more. Hydrogen develops a partial positive charge (δ⁺) because it loses electron density to fluorine.
This makes the H—F bond polar, with one side (fluorine) being more negative and the other side (hydrogen) being more positive. To represent this polarity, the correct notation is:
δ⁺H — Fδ⁻
This notation clearly shows that the hydrogen atom carries a partial positive charge, and the fluorine atom carries a partial negative charge.
This bond polarity is important because it gives the HF molecule a dipole moment, which means the molecule has a positive end and a negative end. This dipole moment contributes to hydrogen fluoride’s physical properties, such as its high boiling point and ability to form hydrogen bonds with other molecules. The polar nature of the bond also affects how HF interacts with other substances, making it a reactive and corrosive chemical in certain conditions.