Polarity of Bonds and Molecules

Flashcards covering definitions and concepts related to bond polarity, molecular polarity, and electronegativity.

What is a polar bond?

A covalent bond in which electron density is shared unequally because one atom is more electronegative, creating a dipole with partial charges (δ⁺ and δ⁻).

What causes a bond to become polar?

A difference in electronegativity between bonded atoms; the more electronegative atom pulls the bonding electrons closer, polarising the bond.

What is electronegativity?

The ability of an atom to attract the bonding pair of electrons in a covalent bond; it increases across a period and decreases down a group in the periodic table.

What is a dipole in the context of chemical bonding?

The separation of charge in a polar bond, where one end carries a slight positive charge (δ⁺) and the other a slight negative charge (δ⁻) due to unequal electron sharing.

How is a dipole represented in a diagram?

With δ⁺ and δ⁻ next to the atoms and an arrow pointing toward the more electronegative atom, often with a cross at the positive tail: e.g., δ⁺H → Clδ⁻.

What is a polar molecule?

A molecule that has an overall dipole because its polar bonds are arranged asymmetrically, so their dipoles do not cancel out.

What is a non-polar molecule?

A molecule that either contains only non-polar bonds (e.g., Cl₂) or has polar bonds arranged symmetrically so their dipoles cancel (e.g., CO₂, CCl₄).

How does molecular shape affect polarity?

Shape determines whether bond dipoles cancel; symmetric shapes (e.g., linear CO₂) can be non-polar, while asymmetric shapes (e.g., bent H₂O) remain polar.

Why is polarisation important in chemistry?

It influences intermolecular forces, solubility (like dissolves like), boiling/melting points, and chemical reactivity.

How can you predict if a bond is polar, non-polar, or ionic?

By electronegativity difference: