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Ch 2
Atoms and Molecules
44
Biology
Undergraduate 1
10/08/2009

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Term
principle chemical elements & functions
Definition

O- component of water. need for cell respiration. in many organic molecules.

N- component of chlorophyll, nucleus acids & proteins.

C- backbone of organic molecules. bonds to 4 atoms

H- component of water. energy transfers

Term
electron configurations with concentric circles
Definition
Bohr model. inaccurate; orbitals extremely large.
Term
atomic mass unit
Definition
amu/dalton. unit of subatomic particle.
Term
isotopes of H
Definition
1 hydrogen. 2 deuterium. 3 tritium
Term
radioisotopes
Definition
unstable & breakdown into other elements. emit beta (B) particle. neutron becomes proton & electron.
Term
autoradiography
Definition
radiation causes dark silver grains in photographic film
Term
radioisotope uses
Definition
tracking stuff through body. dating. cancer- interfere with cell division
Term
principle energy level
Definition
all orbitals in same principle energy level make up the electron shell
Term
electron shell
Definition
one principle energy level
Term
density of an orbital
Definition
proportional to the probability an electron is present there at any given instant
Term
most energetic electrons lie where? least energetic?
Definition
most- outer rings. least- inner rings. because it takes energy to move an electron farther away from charged nucleus.
Term
chemical behavior of an atom determined by?
Definition
valence electrons
Term
isotopes have similar chemical properties bc
Definition
valence shells are identical --> can be substituted in chemical reactions
Term
s orbitals shape? p orbitals shape?
Definition
s- spherical. p- dumbbells. right angles.
Term
avagadro's number
Definition
6.022 x 10^23
Term
structural formula
Definition
formula's arrangement. H-O-H
Term
dynamic equilibrium
Definition
rates of forward & reverse rxn's are equal
Term
covalent bonds
Definition
electrons shared; fill valence shells
Term
what can form 5 bonds?
Definition
phosphorous
Term
orbital hybridization
Definition
orbitals become rearranged when bonds are formed; shape of molecule is changed
Term
electronegativity
Definition
"greediness" for shared electron in a covalent bond.
Term
nonpolar
Definition
electrons are shared equally
Term
polar covalent bond
Definition
electron closer to one atom. positive end & negative end
Term
oxygen forms polar covalent bonds with
Definition
carbon, hydrogen, etc
Term
hydrogen bond
Definition
oxygen, nitrogen, flourine. relatively weak, but strong collectively.
Term
van der waals
Definition
as electrons move around, termpoarily positive & negative ends. operate over very short distances & very weak.
Term
water is polar...
Definition
can form hydrogen bonds with 4 other waters. cohesion (itself), adhesion (others), capillary action (cohesion & adhesion), surface tension (cohesion)
Term
water is an excellent solvent because
Definition
it is polar; can pull ionic compounds apart
Term
hydrophobic molecules
Definition
nonpolar molecules interract with nonpolar molecules. are not disrupted. are insoluble in water, clump together.
Term
kinetic energy
Definition
energy of motion of molecules
Term
difference between heat and temperature
Definition
heat- total kinetic energy in a sample; temperature is average kinetic energy of particles
Term
heat of vaporization? units?
Definition
amount of energy to change 1 g of liquid into vapor. units= calories
Term
calorie
Definition
amount of heat to raise 1 g of water 1 degree Celsius. 4.184 Joules.
Term
water has high specific heat because? what is water's specific heat?
Definition
hydrogen bonding. 1 cal/g of water per degree Celsius.
Term
water expands when it is cooled because
Definition
hydrogen bonding. bonds are formed- crystal lattice
Term
density of water is greatest at__.
above that, ___
Definition
4 degrees C. above that, speed of molecules increases and water expands again.
Term
water ionizes into
Definition
H+ and OH=. becomes H3O+.
Term
ammonia acts as a base how?
Definition
NH3 accepts a proton from water. NH3 + H2O --> NH4+ + OH-
Term
pH
Definition
pH=-log[H+]
Term
[H+][OH-]=
Definition
10^-14
Term
buffer definition. includes?
Definition
resists changes in pH. includes weak acid or weak base.
Term
how buffers work? formula for carbonic acid?
Definition
weak acids. some undissociated molecules are always present. CO2 + H2O --> H2CO3 --> H+ + HCO3-. carbonic acid; bicarbonate. if H+ ions added, combine with HCO3-. OH- ions are added, combine with H+, and more carbonic acid would dissociate.
Term
an acid and a base react to form a
Definition
salt
Term
salt definition
Definition
a compound in which the hydrogen ion of an acid is replaced by some other cation
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