Chemistry Vocabulary These vocabulary words appear on the Chemistry CBA in addition to being tested on the Chemistry Vocabulary Test.
atom the smallest unit of an element that still represents that element.
subatomic particle the particles that make up an atom: protons, electrons, and neutrons.
neutron A neutral particle in the nucleus of an atom that has a mass of 1 amu.
proton positively charged particle in the nucleus of an atom that has a mass of 1 amu.
nucleus the positively charged region in the center of an atom where most of an atom s mass is located; contains protons and neutrons. Mass = Protons + Neutrons
electron a negatively charged particle that occupies the space in an atom outside the nucleus and has almost zero amu.
the electrons in the outermost shell (orbital) of an atom that participates in chemical bonding. valence electron
electron cloud the region surrounding an atom s nucleus where one or more electrons are most likely to be found.
energy level The general region of the electron clouds where specific numbers of electrons are located; also called orbitals.
electron dot diagram Also called Lewis Structure ; a model that represents valence electrons in an atom as dots around the element s chemical symbol.
atomic number the number of protons in an atom of an element. A = P = E Atomic Number = Protons = Electrons** **for a neutral atom
mass number the sum of the number of protons and neutrons in an atom. M-A =N Mass Atomic Number = Neutrons
average atomic mass the average mass of the element s isotopes, weighted according to the abundance of each isotope.
atomic mass unit (amu) the unit used to measure atomic mass which is equal to 1.6727 x 10-24 grams.
isotopes atoms of the same element that have different numbers of neutrons.
ion an atom that is no longer neutral because it has gained or lost electrons.
positively charged atom When a neutral atom loses one or more negatively charged electron(s) and becomes positively charged due to having more protons (+) than electrons (-).
negatively charged atom When a neutral atom gains one or more negatively charged electron(s) and becomes negatively charged due to having more electrons (-) than protons (+).
radioactive any element that spontaneously emits radiation.
periodic table a chart of the elements arranged into groups (columns) and periods (rows) according to their physical and chemical properties.
group also called a family ; a vertical column on the periodic table containing elements that have similar reactivity and other chemical properties due to equivalent number of valence electrons.
period a horizontal row on the periodic table containing elements with the same number of energy levels (orbitals); but elements do not necessarily have similar properties.
chemical bond a force that holds two or more atoms together due to elements sharing or transferring electrons to other elements.
ionic bond the chemical bond formed due to the attraction between positively and negatively charged ions in an ionic compound.
covalent bond a chemical bond formed due to the sharing of valence electrons in a covalent compound.
molecule A group of atoms chemically bonded together that represents the smallest unit of a compound
chemical formula an expression that indicates the number and types of elements that a molecule is composed of
subscript The small number next to the symbol of an element that indicates the number of atoms present in the chemical formula
chemical reaction a process in which atoms of one or more substances rearrange to form one or more new substances with new physical and chemical properties; a chemical change.
chemical equation a description of a chemical reaction using element symbols and chemical formulas.
reactant The initial substance(s) in a chemical reaction; the elements that react.
product The resulting substance(s) that are produced by a chemical reaction.
coefficient a large number placed in front of an element symbol or chemical formula in an equation that represents the number of molecules.
balanced chemical equation A chemical equation with the same amount of atoms from each element on either side of a chemical equation
Law of Conservation of Mass law that states that the total mass of the reactants before a chemical reaction is the same as the total mass of the products after the chemical reaction; also referred to as The Law of Conservation of Matter.