biol 1107 ch 2: the chemistry of life

atoms

simplest units of matter

protons

positive charge & found in the nucleus

neutrons

no charge & found in the nucleus

isotopes

atoms with the same number of protons but different numbers of neutrons

electrons

negative charge & not found in nucleus

atomic number

number of protons

atomic mass

approximately equal to protons & neutrons → # with decimals

ions

atoms that have gained or lost electrons

chemical bonding

how molecules are formed

valence shell

outermost layer of electrons → involved in forming bonds

octet rule

atoms are most stable when their valence shell is full with 8 electrons

ionic bond

form when 1 atom donates an electron to another

covalent bonds

form when atoms share pairs of electrons in their valence shell

nonpolar

electrons are evenly shared between atoms → no partial charges

polar

electrons are unevenly shared → results in partial charges

hydrogen bonds

form between molecules and occur when negatively charged pole of 1 molecule is attracted to the positively charged pole of another

high heat capacity / high heat of vaporization

H2O heats & cools very slowly

universal solvent

H2O will dissolve other polar molecules & ionic components

cohesion

H2O molecules will cling to each other

adhesion

H2O molecules will cling to other surfaces

surface tension

H2O behaves as if coated with an invisible film

capillary action

H2O molecules will climb their way up a thin tube

dissociation

H2O molecules will spontaneously split & reform H2O

pH

a measurement of the concentration of H+ in a solution

acids

increase H+, decrease pH level

bases

decrease H+, increase pH

buffers

can accept H+ when two plentiful or donate H+ when too few

carbon (organic molecules)

any molecules that contains carbon

isomers

molecules that have the same chemical formula, but different arrangements, different orientations, or are mirror images

structural isomers

have same chemical formula but different arrangements of atoms

geometric (cis/trans) isomers

same chemical formula, same arrangement of atoms but different orientations around a double bond

enantiomers

same chemical formula, same arrangement of atoms, same orientation, but are mirror images