Lecture 1

What are the two most common elements in biology?

Hydrogen and carbon

What is the atomic number of an element?

The number of protons in an atom, which gives the element its identity.

What is the mass number of an element?

The number of protons plus neutrons in an atom.

What unit is used for atomic mass?

Dalton (Da or D)

What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons.

What type of bond forms when atoms share electrons?

Covalent bond

What happens during the formation of a covalent bond?

Two electrons are shared, one from each atom.

What determines the shape of a molecule?

The shape of the orbitals that make up the covalent bonds.

What is electronegativity?

A measure of how strongly electrons are attracted to the nucleus.

What is a nonpolar covalent bond?

A bond where electrons are equally distributed between atoms.

What is a polar covalent bond?

A bond where electrons are not equally distributed, leading to partial charges.

What is the consequence of polar covalent bonds in water?

The formation of hydrogen bonds.

What property of water explains how it can rise in trees?

Cohesion.

Why is liquid water denser than ice?

To allow survival of larger organisms in lakes.

How does water moderate temperature?

Through hydrogen bond formation or disruption which buffers heat energy.