UWG Principles of Biology Chapters 2-3

“Elements of Life”

Oxygen, Carbon, Hydrogen, Nitrogen

Elements’ properties depend on

Atoms

Atoms are made of prots/neuts/elects, which subatomic particles compose the nucleus?

Protons, Neutrons

Atomic number

Number of protons

Chemical behavior of atom depends mostly on electron no. in

valence shell (outermost)

Mass number is..

Twice the atomic number; sum of protons & neutrons

Chemical bonds

Attractive force linking 2 or more atoms together

Covalent bonds

Type of chem. bond where a pair of valence electrons are shared by two atoms filling their valence shell

What’s this bond?

Single bond - 1 pair of electrons shared

What’s this bond?

Double bond - 2 pairs of electrons shared

What’s this bond?

Triple bond - 3 pairs of electrons shared

Unequal sharing of electrons occurs within molecules due to

electronegativity

Nonpolar covalent bond

Atoms share electrons equally

Polar covalent bond

One atom more electroneg; unequal sharing

Ions

Form when atoms gain or lose 1 or more electron

Cations

positively charged ions

Anions

negatively charged ions

Hydrogen bonds

Bond between partial positive & partial negative charges on hydrogen atom of water molecule

Cohesion

Water molecules clinging to each other (via hyd bonds)

Adhesion

Water molecules clinging to external substances

Heat is ___ when hydrogen bonds break

Absorbed

Heat is ___ when hydrogen bonds form

absorbed

High Specific Heat

Amt. of heat energy required to raise temperature of 1g substance by 1 Celsius