the zero point on the Kelvin temperature scale, equivalent to -273.15 degrees C; all molecular motion theoretically stops at this temperature.
a compound that produces hydrogen ions in solution, is a hydrogen-ion donor, or an electron-pair acceptor.
any solution in which the hydrogen-ion cncentration is greater thatn the hydroxide-ion concentration.
one of two or more different molecular forms of an element in the same physical state; oxygen and ozone are allotropes of the element oxygen.
a positively charged particle emitted from certain radioactive nuclei; it consists of two protons and two neutrons and is identical to the nucleus of a helium atom.
atomic emission spectrum
the pattern of frequencies obtained by passing light emitted by atoms of an elelment in the gaseous state through a prism; the emission spectrum of each element is unique to that element.
a region in space around the nucleus of an atom where there is a high probability of finding an electron.
equal volumes of gases at the same temperature and pressure contain equal numbers of particles.
the number of representative particles contail in one mole of a substance; equal to 6.02 X 10^23 particles.
a chemical equation in which mass is conserved; each side of the equation has the same number of atoms of each element.
any solution in which the hydroxide-ion concentration is greater than the hydrogen-ion concentration.
a fast-moving eleron emitted from certain radioactive nuclei; it is formed whn a neutron decomposes into a proton and an electron.
a substance that increases the rate of reaction by lowering the activation-energy barrier; the catalyst is not used up.
a stream of electrons produced at the negative electrode (cathode) of a tube containing a gas at low pressure.
the temperature scale on which the freezing point of water is 0 degrees Celcius, and the boiling point is 100 degrees Celcius.
an expression representing a chemical reaction; the formulas of the reactants (on the left) are connected by an arrow with the formulas for the products (on the right)
a state of balance in which forward and reverse reactions are taking place at the same rate; no net change in the amounts of reactants and products occurs in the chemical system.
shows the number and type of atoms present in the smallest representative unit of a substance; the chemical formula of ammonia, with one nitrogen and three hydrogens, in NH3.
the ability of a substance to undergo chemicl reactions and to form new substances.
the changing of substances to other substances by breaking of bonds in reactants and the formation of bonds in products.
the study of the structure, properties, and composition of substances, and the changes that susbtances undergo.
a mixture who particles are intermediate in size between those of a suspension and a solute solution.
a chemical change in which two or more substances react to form a single new substance; also called a synthesis reaction.
a chemical change in which oxygen reacts with another substance, often producing energy in the form of heat and light.
a substance that can be separated into simpler substances (elements or other compounds) only by chemical reactions.
a measurement of the amount of solute that is dissolved in a given quantity of solvent; usually expressed as mol/L.
condensed structural formula
a structural formula that leaves out some bonds and/or atoms the presence of these atoms or bond is understood.
a ration of equivalent measurements used to convert a quantity from one unit to another.
Dalton's atomic theory
the first theory to relate chemical changes to events at the atomic level.
de Broglie's equation
an equation that describes the wavelength of a moving particle; it predicts that all matter exhibits wavelike motions.
a chemical change in which a single compound is broken down into two or more simpler products.
the tendency of molecules and ions to move toward areas of lower concentration until the concentration is uniform throughout the system.
a technique of problem-solving that uses the units that are part of a measurement to help solve the problem.
a chemical change involves an exchange of positive ions between two compounds.
the arrangement of electrons around the nucleus of an atom in its ground state.
a substance that cannot be changed into simpler substances under normal laboratory conditions.
a formula with the lowest whole-number ration of elements in a compound; the empirical formula of hydrogen peroxide (H2O) is HO.
the capacity for doing work; it exists in several forms, including chemical, nuclear, electical, rdiant, mechanical, and thermal energies.
the lowest whole-number ration of ions in an inic compound; in magnesium chloride, the ration of magnesium ions to chloride ions is 1:2 and the formula unit is MgCl2.
the number of wave cycles that pass a given point perunit of time; there is an inverse relationship between the frequency and the wavelength.
high energy electromagnetic radiation emitted by certain radioactive nuclei; gamma rays have no mass or electrical charge.
gram atomic mass (gam)
the mass, in grams, of one mole of atoms in a monoatomic element; it is numberically equal to the atomic mass in amu.
a vertical colum of elements in the periodic table; the constituent elements of a group have similar chemical and physical properties.
a mixture that is not uniform in compositionl its componenets are not readily distinguished.
a mixture that is completely uniform in composition; its components are not readily distinguished.
when electrons occupy orbitals of equal energy, one electron enters each orbital until all orbitals contain one electron with their spins parallel.
a relatively strong intermolecular force in which a hydrogen atom that is covalently bonded to very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom in the same molecule or one nearby.
International System of Units (SI)
the revised version of the metric system, adopted by international agreement in 1960.
an atom or group of atoms that has a positive or negative charge; cations are ions with a positive charge, and anions are ions with a negative charge.
atoms of the same element that have the same atomic bumber but different atomic masses due to a different number of neutrons.
the temperature scale in which the freezing point of water is 273 K and the boiling point is 373 K; 0 K is absolute zero.
law of conservation of energy
energy that is neither created nor destroyed in an ordinary chemical or physical process.
law of conservation of mass
mass can be neither created nor destroyed in an ordinary chemical or physical process.
law of definite proportions
in any sample of a chemical compound, the elements are always combined in the same proportion by mass.
the volume of a cube measuring 10 centimeters on each edge (1000 cm cubed); it is the common unprefixed unit of volume in the metric system.
the temperature at which a substance changes from solid to a liquid; the melting point of water is 0 degrees Celcius.
one of a class of elements that includes a large majority of the known elements; metals are characteristically lustrous, malleable, ductile, and good conductors of heat and electricity.
the force of attraction that holds metals together; it consists of the attraction of free-floating valence elecrons for positively charged metal ions.
a general expression used to refer to the mass of a mole of any substance unless a more specific term is needed to avoid confusion.
the amount of a substance that contains 6.02 X 10^23 representative particles of that substance.
a chemical formula that shows the actual number and kinds of atoms present in a molecule of a compound.
an orbital resulting from the overlapping of atomic orbitals when two atoms combine.
net ionic equation
an equation for a reaction in solution showing only those particles that are directly involved in the chemical change.
any member of a group of gaseous elements in Group 0 of the periodic table; the s and p sublevels of their outermost energy level are filled.
one of a class of elements that are not lustrous and are generally poor conductors or heat and electricity; non-metals are grouped on the right side of the periodic table.
information obtained through the senses; observation in science often involves a measurement.
a process that involves complete or partical loss of electrons or a gain of oxygen; it results in an increase of the oxidation number of an atom.
Pauli exclusion principle
no more than two electrons can ocupy an atomic orbital; these elctrons must have opposite spins.
the ratio of the actual yield to the theoretical yield for a chemical reaction expressed as a percentage; a measure of the efficiency of a reaction.
when the elements are arranged in order of increasing atomic number, there is a period repition of their physical and chemical properities.
an arrangelment of elements into row and columns according to similarities in their properties.
a number used to denote the hydrogen-ion concetraion, or acidity, of a solution it is the negative logarithm of the hydgrogen-ion concetration of a solution.
electrons are ejected by certain metals when they absorb light with a frequency above a threshold frequency.
a quality of a substance that can be observed or measured without changing the substance's chemical composition.
Planck's constant (h)
a number used to calculate the radiant energy (E) absorbed or emitted by a body based on the frequency of radiation.
a bond formed when two different atoms are joined by a covalent bond and the bonding electrons are shared unequally.
a molecule, like water, in which one or more atoms is slightly negative and one or more is slightly positive, unless molecular geometry causes the polarieis to cancel each other out.
the amount of energy needed to move an electron from its present energy level to the next higher one.
quantum mechanical model
the modern description, primarily mathematical, of the behavior of electrons in atoms.
the spontaneous emission of radiation by an unstable nucleus; the rate of decay is unafected by temperature, pressure, or catalyst.
a series of elementary reactions that take place during the course of a complex reaction.
a process that involves a complete or partial gain of electrons or the loss of oxygen; it results in a decrease o the oxidation number of an atom.
Group A element on the periodic table; together, these elements, which have only partially filled outermost s and p sublevels, illustrate the entire range of chemical properties.
the smallest unit into which a substance can be broken down without a change in composition; the term refers to wherther a substance commonly exists as atoms, ions, or molecules.
a reaction in which the conversion of reactants into products and the conversion of products into reactants occur simultaneously.
a solution containing the maximum amount of solute for a given amount of solvent at a constant terperature and pressure; an equalibrium exists between undissolved solute and ions in solution.
a method of inquiry involving observation, experiements, hypotheses, and broad explanations.
all the digits that can be known precisely in a measurement, plus a last estimated digit.
a chemical change in which one element replaces a second element in a compound; also called displacement reaction.
a chemical equation that does not indicate the relative amounts of reactants and products.
the amount of a substance that dissolves in a given quantity of solvent at specified conditions fo temperature and pressure to produce a saturated solution.
the ratio of the density of a substance to that of a standard substance (usually water).
an ion that is not directly involved in a chemical reaction; an ion that does not change oxidation number or compostioni during a reaction.
range of wavelengths of electromagnetic radiation; wavelengths of visible light are separated when a beam of white light passes through a prism.
standard temperature and pressure (STP)
the conditions uner which the voume of a gas is usually measured; standard temperature is 0 degrees Celcius, and standard pressure is 1 atmosphere (atm).
a base that completely dissociates into metal ions and hydrroxide ions in aqueous solution.
a chemical formula that shows the arrangement of atoms in a molecule or a polyatomic ion; each dash between two toms indicates a pair of shared electrons.
an atom or group of atoms that can take the place of a hydrogen atom on a parent hydrocarbon molecule.
common type of organic reaction; involved the replacement of an atom or group of atoms by another atom or group of atoms.
a measure of the average kinetic energy of particles in matter; temperature determines the direction of heat transfer.
a compound containing atoms of three different elements, usually containing at least on epoluatomic ion; Na2CO3 and Mg(OH)2 are ternary ionic compounds.
the amount of product that could form during a reaction calculated from a balanced chemical equation; it represents the maximum amount of product that could be formed from a given amount of reactant.
an element in the periodic table with an atomic number that is greater than 92.
scattering of light by particles in a colloid or suspension, which causes a bean of light to become visible.