Chemistry
Study of the composition, properties, and changes of substances
Precision
Measure of the agreement between the numerical values of 2 or more measurements
Accuracy
Indication of how close a measurement is to its accepted value
significant digit
Digit in a measurement that is certain, plus one digit that is an estimate
density
Mass of an object divided by its volume
mass (vs. weight)
Quantity of matter in an object; independent of gravity
dimensional analysis
Technique for converting between units
absolute zero
Theoretically lowest temp that can be reached, -273 �C or 0 K
law of conservation of energy/mass/matter
Energy, mass, or matter is neither created nor destroyed in any process
chemical property
Cannot be observed without altering the identity of the substance
physical property (extensive vs. intensive)
Can be observed w/o altering identity; ext. depends on amount
chemical change
Process producing a new substance
physical change
Non-altering identity process
element
Simplest type of pure substance
compound
2 or more elements chemically combined in a fixed proportion
heterogeneous mixture
Particles not uniformly mixed; visibly different parts
homogeneous mixture
Uniformly mixed particles; solutions electron negatively charged subatomic particle proton positively charged subatomic particle
neutron
neutral subatomic particle
isotope
atom of an element with the same number of protons but a different number of neutrons
mass number
sum of the protons + neutrons
atomic mass unit
1/12 the mass of a carbon-12 atom
atomic number
number of protons in the nucleus of an atom
amplitude
height of a wave measured from its origin to its crest
wavelength
distance between 2 successive similar points on a wave (?)
frequency
# of waves that pass a certain point in a given amount of time (Hz)
quantum
smallest unit of radiant energy that can be absorbed or emitted
period
horizontal row of elements on the periodic table
group
(family) vertical column of elements on the periodic table
valence electrons
outermost energy level electrons; gained, lost, or shared in the formation of chemical bonds
atomic radius
distance between the center of the nucleus and the outermost electrons of an atom
ionization energy
energy needed to remove the most loosely held electron from an atom
electronegativity
tells how strongly an atom attracts electrons in a chemical bond
Rutherford
gold foil; mostly empty space w/ + dense core (nucleus) and orbiting electrons
Thomson
with CRT discovered electrons
Planck
quantum theory; E = hv
Heisenberg
uncertainty principle
Dalton
1st modern atomic theory
Moseley
atomic number
Millikan
oil drop; charge of the electron
Bohr
spectral lines for Hydrogen; electrons found in specific (quantized) energy levels
ionic bond
formed by transfer of electron(s); metal + nonmetal
formula unit
used to designate a unit of an ionic compound
covalent bond
formed by sharing electrons; nonmetal + nonmetal
molecule
neutral group of atoms united by covalent bonds
cation
positive ion ; metals losing e-'s
anion
negative ion ; nonmetals gaining e-'s
octet
rule gaining, losing, or sharing electrons to obtain a full outermost
energy level, typically 8 e
's; noble gas configuration
interparticle force
weak attraction existing between neighboring particles (e.g., ions, molecules, atoms) 10
intermolecular force
weak attraction existing between neighboring molecules; also called Van der Waals forces
induced dipole
created (within a nonpolar molecule) by the presence of a neighboring dipole or ion
dispersion force
intermolecular force of attraction between induced dipoles (between nonpolar molecules)
dipole dipole force
between neighboring dipoles; line up with positive and negative ends close to each other
hydrogen bond
between hydrogen atom of one molecule and a highly electronegative atom of another molecule; accounts for surface tension of water
ion dipole
force between an ion and a polar molecule; positive end of dipole attracted to negative ions and negative end of dipole attracted to positive ions
atomic mass
average of the masses of all isotopes of an element
formula mass
sum of the masses of all the atoms in a compound
molar mass
mass in grams of one mole of a substance