Glossary

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acid-base reactions a broad definition can include all ionic reactions...a more restricted definition is the transfer of a proton between two reactants

alpha particle nucleus of a helium atom given off during radioactive decay

amphoteric capable of reacting with both acids and bases

anion ion that has negative charge

anode positively charged electrode

Arrhenius acid base theory acids are proton donors and bases are hydroxide donors

atom the smallest division of matter that retains identity

atomic number number of protons in the nucleus of an atom

atomic mass the total number of neutrons and protons in the nucleus of an atom...usually given as an average mass which includes isotopes

Avogadro's number 6.023x10²³ molecules

beta particle an energetic electron given off during radioactive decay

bond polarity property of a bond determined by the electronegativity difference between the two atoms

Bronsted acid-base theory acids are proton donors and bases are proton acceptors

buffer solution is a solution that resists a change in pH when small amounts of an acid or base are added to the solution

calorie is a unit of energy equal to the amount of heat needed to raise the temperature of one gram of water one degree centigrade

Calorie is equal to 1000 calories

catalyst a chemical substance that increases the speed of a chemical reaction without undergoing permanent change

cathode a negatively charged electrode...the electrode at which reduction occurs

cation ion that has positive charge

chain reaction a self sustaining reaction

chemical bond the attractive force that holds atoms together in molecules

chemical change a change in the chemical structure or composition of a substance

chemical equation a description of a chemical reaction that uses formulas and coefficients to indicate the number of moles of each compound

chemical formula representation with symbols and subscript numbers of the numbers of atoms combined in a chemical compound

chemistry the study of the nature, properties and transformations of matter

combination reaction is a reaction where two or more reactants (elements or compounds) react to form only a single product

compounds pure substances made up of two or more atoms in a fixed combination and composition

conjugate acid the species formed when a base reacts with a proton

conjugate base the species left after an acid gives up a proton

Coulomb's Law expression for the force between two charged bodies

covalent bond the equal sharing of electrons between two atoms

critical mass the amount of fissionable material necessary to sustain a chain reaction  

Dalton's Atomic Theory early theory of the structure of atoms

decomposition reaction is a reaction where a single compound undergoes a reaction to form two or more products

density the ratio of mass per volume of a substance

dimensional analysis a process of problem solving that utilizes conversion factors rather that mathematical formulas

dipole partial positive and partial negative charges separated by a distance

dipole-dipole interaction attraction between two polar molecules

double bond a covalent bond that results from the sharing of two pairs of electrons between two atoms

double replacement reaction is a reaction where two positive ions exchange partners

electrochemical cell a device that produces electricity from an oxidation-reduction reaction

electromagnetic radiation a form of energy that has wave characteristics and that propagates through a vacuum at the speed of 3.0 x 10¹⁰ cm/s

electromagnetic spectrum the distribution of frequencies of radiation

electron subatomic particle having essentially no mass and a negative charge

electron configuration   specific arrangement of an atom's electrons in energy levels

electron-dot formulas structural formula of a molecule that also includes the valance electrons

electronegativity the attraction of a nucleus for electrons

element a pure substance that cannot be broken down into simpler substances by ordinary chemical changes

energy the capacity to do work or supply heat

equilibrium constant a number representing the ratio of products to reactants in an equilibrium reaction

equilibrium reaction a chemical reaction where the forward reaction to products is balanced by the reverse reaction back to the reactants

formal charge the magnitude and sign of the charge on an atom

gamma radiation electromagnetic radiation of extremely short wavelength given off during radioactive decay

gram the metric system standard unit of weight

greenhouse effect the warming of the earth by reemitted infrared radiation

half-life the time required for the radioactive decay of one half of the atoms of a radioactive substance

hydrogen bond attraction between an electron deficient hydrogen (bound to a highly electronegative atom) and non-bonding electrons on other atoms

hydronium ion the ion formed by the reaction of water and a proton, H₃O⁺  

hypothesis educated guess concerning the cause of an observed phenomenon that is still unproven by experimentation

inert gases elements that have an outer filled electron energy level or shell

ion an atom that has gained or lost an electrons and has a negative or positive charge

ionic bond the transfer of an electron from one atom to another atom

isotopes atoms of the same element that have different numbers of neutrons in the nucleus

limiting reagent that chemical reactant that limits the extent of a reaction

liter the metric system standard unit of volume

mass a given quantity of matter regardless of the force of gravity

matter anything that occupies space and has mass

meter the metric system standard unit of length

mixture a physical combination of two or more substances

molarity definition of the concentration of a solution in moles per liter

molecular formula chemical formula that gives the composition of one molecule

molecule a non-ionic compound consisting of two or more atoms combined in a fixed ratio of whole numbers

moles a defined quantity of a substance equal to the molar mass in grams

neutron a subatomic particle having no charge and a mass of one amu

non-bonding electrons valence electrons on an atom that are not involved in a chemical bond

nuclear fission the breaking apart of atomic nuclei into smaller nuclei accompanied by the release of energy

nuclear fusion the combination of two or more light nuclei to yield a heavier nucleus

nuclear reactions changes in the composition of the nucleus of an atom

nucleus the hard dense core of an atom that contains neutrons and protons

octet rule elements are more stable if they have an inert gas configuration

orbitals probability areas in space around the nucleus of an atom where electrons may be found

osmosis the passage of solvent molecules, but not solute molecules, through a semi-permeable membrane

oxidation is the loss of an electron or electrons by an atom

oxidation-reduction reactions reactions that involve the transfer of an electron between two reactants

oxidizing agent the species in an oxidation-reduction reaction that is reduced

periodic table a device that organizes elements by electron configuration

pH negative logarithm of the hydronium ion concentration

photon a unit of energy of radiation equal to hn where h is Planck's constant (6.6261 x 10^-34 Jsec) and n is the frequency of the radiation equal to the speed of light (2.9979 x 10⁸ m/s) divided by the wavelength of the light

physical change a change in the solid, liquid or gas state of matter

polar-covalent bond the unequal sharing of electrons between two atoms

proton a subatomic particle having a positive charge and a mass of one amu

radioactive decay  term for the process in which the nuclei of certain atoms disintegrate and emit radiation

radioisotopes  elements that have unstable nuclei that will undergo radioactive decay

reducing agent the species in an oxidation-reduction reaction that is oxidized

reduction is the gain of an electron or electrons by an atom

scientific method the observation, explanation and testing of an explanation by repeatable experiments

scientific notation the representation of a quantity as a decimal number between one and ten multiplied by ten raised to a power

semiconductor a material that does not normally conduct electricity but will if energy is applied in some fashion...these may be n-type or p-type

single replacement reaction is a reaction where one element reacts with a compound and replaces another element in that compound

solute substance being dissolved in a solution

solution the liquid (solvent) in which some substance (solute) is dissolved

solvent liquid that causes another substance to dissolve

stoichiometry the process by which the quantities of the substances involved in a chemical reaction are related and calculated

STP standard temperature and pressure equal to 237 K and 1 atm

structural formulas depiction of a molecule that shows the atoms in their correct placement

theory rational explanation for a phenomenon that is supported by repeatable experiments

triple bond a covalent bond in which three pairs of electrons are shared between two atoms

valence electrons the outermost electrons of an atom

wavelength the distance between crests in the wavelike oscillations of electromagnetic radiation