Bond polarity NAT

Electronegativity definition

The power of an atom to attract a pair of electrons in a covalent bond towards itself

Electronegativity Trend

- increases across a period (atomic radius decreases)

- decreases down a group (shielding increases)

How does a permanent dipole form?

- if two bonded atoms have different electronegativities

- more electronegative atoms draws more negative charge towards itself

Explain how permanent dipole-dipole forces arise between hydrogen chloride molecules. (2)

- Difference in electronegativity leads to bond polarity

- (dipoles don't cancel so the molecule has an overall permanent dipole) and there is an attraction between ∂+ on one molecule and ∂- on another

How does induced dipole form?

- when electron orbitals around molecule influenced by another charged particle

C-Br bond is polar

Why is CBr4 not a polar molecule (2)

- molecule completely symmetrical/molecule is tetrahedral

- dipoles cancel out

How do hydrogen bonds form between O and H. (2)

- electron deficient H

- attracts lone pair/electron pair on O

Suggest why chloroethanoic acid is stronger acid than ethanoic acid. (3)

- Cl is electron withdrawing group/negative inductive effect

- weakens O-H bond / increases polarity of O-H bond