The Elements of Life (Polarity)

How many valence electrons does carbon have and how many bonds can it form?

Carbon has 4 valence electrons and can form 4 bonds.

What types of bonds and structures can carbon form?

Carbon can form single, double, or triple bonds and can make long or short chains, with or without branching.

Why is carbon important in biology?

Carbon is the backbone of biological and organic molecules; all living organisms are made of carbon-based chemicals.

What are hydrocarbons?

Compounds made of only hydrogen and carbon; they form the basis of most biological molecules.

What does it mean if a carbon’s fourth bond isn’t shown in a diagram?

It’s assumed to be bonded to hydrogen.

What are functional groups?

Chemically reactive groups attached to the carbon skeleton where reactions occur.

How do functional groups affect molecules?

They give molecules distinctive properties and influence their shape and reactivity.

Why are most functional groups polar?

Because they contain nitrogen or oxygen, which are electronegative atoms.

How do functional groups affect solubility?

More functional groups → more polarity → more hydrophilic (water-loving).

Few or no functional groups → more hydrophobic (water-fearing).

What happens to carboxyl and amino groups at normal cellular pH?

They ionize (gain or lose charges).

When is a bond polar?

When the difference in electronegativity between atoms is greater than 0.4.

What causes a dipole moment?

Unequal sharing of electrons—one end becomes slightly positive, the other slightly negative.

How do polar molecules interact with each other?

Opposite charges attract; like charges repel.

How do polar and nonpolar molecules differ in electron sharing?

Polar molecules share electrons unequally; nonpolar molecules share electrons equally.

Do polar molecules have a dipole moment?

Yes, polar molecules have a dipole moment; nonpolar molecules have none (zero).

What is the electronegativity difference in polar vs nonpolar molecules?

Polar molecules have a difference greater than 0.4; nonpolar molecules have a difference less than 0.4.

How do the boiling and melting points of polar and nonpolar molecules compare?

What kind of charge separation exists in polar vs nonpolar molecules?

Polar molecules have partial positive and negative charges; nonpolar molecules have no charge separation.

What types of intermolecular forces do polar and nonpolar molecules have?

Polar molecules form hydrogen bonds; nonpolar molecules have weak van der Waals forces.