the law that states that mass cannot be created or destroyed in ordinary chemical and physical changes.
law of definite proportions
the law that states that a chemical compound always contains the same elements in exactly the same proportions by weight or mass.
law of multiple proportions
the law that states that when an element combines to form two or more compounds, the mass of the element that combines with a given mass of the other is in the ratio of small whole numbers.
atom
the smallest unit of an element that maintains the chemical properties of that element.
nuclear forces
the interaction that binds protons and neutrons, protons and protons, and neutrons and neutrons together in a nucleus.
atomic number
the number of protons in the nucleus of an atom.
average atomic mass
the weighted average of the mass of all naturally occurring isotopes of an element.
mass number
the sum of the numbers of protons and neutrons in the nucleus of an atom.
electromagnetic spectrum
all of the frequencies or wavelenghts of electromagnetic radiation.
excited state
a state in which an atom has more energy than it does at its ground state.
frequency
the number of cycles or vibrations per unit of time; also the number of waves produced in a given second of time.
ground state
the lowest energy state of a quantizied system.
wavelength
the distance from any point on a wave to an identical point on the next wave.
angular momentum quantum number
the quantum number that indicates the shape of an orbital
Heisenberg Uncertainty Principle
the principle that states that determining both the position and velocity of an electron or any other particle simultaneously is impossible.
magnetic quantum number
the quantum number that corresponds to the alingment of the angular momentum component with a magnetic field.
orbital
a region in an atom where there is high probability of finding electrons.
principal quantum number
the quantum number that indicates the energy and orbital of an electron in an atom.
quantum numbers
a number that specifies the properties of electrons.
quantum theory
the study of the structure and behavior of the atom and of subatomic particles from the view that all energy comes in tiny indivisible bundles.
spin quantum numbers
the quantum number that describes the intrinsic angular movement of a particle.
Aufbau principle
the principle that states that the structure of each successive element is obtained by adding one proton to the nucleus of the atom and one electron to the lowest-energy orbital that is available.
electron configuration
the arrangement of electrons in an atom.
Hund's rule
the rule that states that for an atom in the ground state, the number of unpaired electorns is the maximum possible and those unpaired electrons have the same spin.
noble gases
one of the elements of group 18 of the periodic table; are unreactive.
Pauli exclusion principle
the principle that states that two particles of a certain class cannot be in exactly the same energy state.
highest occupied level
the electron-containing main energy level with the highest principal quantum number.
inner-shell electrons
electrons that are not in the highest-occupied energy level.
noble-gas configuration
an outer main energy level fully occupied, in most cases, by eight electrons.