Atoms, Bonds, Water & pH

Electronegativity

An atom's ability to attract shared electrons.

What happens to shared electrons near a more electronegative atom?

They spend more time near that atom.

Polar covalent bond

Electrons are shared unequally.

Nonpolar covalent bond

Electrons are shared relatively equally.

What causes partial charges in a covalent bond?

Unequal electron sharing due to electronegativity differences.

What does δ− indicate?

Partial negative charge.

What does δ+ indicate?

Partial positive charge.

Ionic interaction

Attraction between opposite full charges.

Hydrogen bond

Attraction involving a δ+ H and an electronegative/δ− region.

Van der Waals interactions

Weak attractions caused by temporary charge distributions.

Why is water polar?

O attracts shared electrons more strongly than H.

What charge does O have in water?

Partial negative (δ−).

What charge does H have in water?

Partial positive (δ+).

Why can water molecules hydrogen-bond?

δ+ H on one molecule is attracted to δ− O on another.

Hydrophilic

Polar/charged and interacts favorably with water.

Hydrophobic

Nonpolar and interacts poorly with water.

Which molecules generally interact best with water?

Charged and polar molecules.

Acid

Increases H+ concentration.

Base

Accepts/decreases H+.

What happens to H+ when pH decreases?

H+ concentration increases.

Buffer

Resists changes in pH.