Chemistry of Life

Essential Elements of Life

96% of the mass of all living things made up of 4 elements : oxygen,carbon,hydrogen,nitrogen

Trace Elements

IRon, Iodine, Copper

protons

packed with neutrons in nucleus, positively charged, most atoms have the same amount of portons as electrons making their electrically neutral

neutrons

packed with protons in nucleus, no charge,

isotopes

same element with different amount of neutrons in nucleus, vary in mass, gives off particles and energy

Electrons

negatively charged, very small,

valence electrons

are those in the outermost shell

electron shell

electron’s state of potential energy is called its energy level

atomic number

protons in nucleus

mass number

protons + neutrons, average of al isotopes

Ionic bonds

nonmetal + metal

one of more electrons is transferred from atom to another

one atom loses electrons (becomes positively charged) while the other gains electrons (becomes negatively charged)

results from attraction of two oppositely charged ions (cations + anions)

cation

positive charge

anion

negative charge

Covalent bonds

nonmetal + nonmetal

formed when electrons are shared between atoms

nonpolar covalent bond

electrons are shared equally

polar covalent bond

electrons are shared unequally

single covalent bond

one pair of electrons is shared

double covalent when 2 pairs are shared

structural formula

used to represent atoms and bonding

ex. H-H

Molecular formula

abbreviated structural formula

H2

electronegativity

is an atom’s attraction for the atoms in a covalent bond

The more electronegative an atom, the more strongly it pulls shared electrons itself

Hydrogen bonds

hydrogen atom covalently bonds to one electronegative is also attracted to another electron atom

Hydrogen bonds are usually oxygen or other nitrogen atoms

Van der Waals Interactions

weakest

If electrons are distributed asymmetrically in molecules or atoms, they can result in “hot spots” of positive or negative charge

attractions between molecules that are close together as a result of these charges

hydrogen bonds

a weak intermolecular force that occurs between two electronegative atoms, such as nitrogen and oxygen, with a hydrogen atom in between.

Lends water many special properties

1. cohesion (tendency of water to stick to water)

2. adhesion (tendency of water to stick to other substances)

3. surface tension (results from cohesion of water molecules)

4. high heat capacity (allows organisms to keep constant body temp)

5. high heat of vaporization (heat a liquid must absorb for 1g to be converted to gas)

6. expansion of freezing

7. versatility as a solvent

acidic

a solution is acidic if it contains a lot of H+

ACIDS 1-7 pH Bases 7-14 pH

alkaline

a solution is alkaline if it contains a lot of OH-

organic compound

contains carbon

Inorganinc compound

does not contain carbon

polymers

most macromolecules are chains of building blocks

polymers

individual blocks of monomers

contains carbon,hydrogen, and oxygen 1:2:1 ratio

monosaccharides

glucose and fructose

polypeptide

multiple amino acids