matter

anything that occupies space and has mass

element

a pure substance that cannot be broken down into other substances by chemical reactions

compound

substance containing two or more elements chemically combined in a fixed ratio

atom

the smallest particle of an element that retains the properties of the element

proton

subatomic particle having a positive charge; found in nucleus

electron

subatomic particle having a negative charge; not in nucleus but surrounds it

neutron

subatomic particle without a charge; found in nucleus

nucleus

protons and neutrons together; make up the center of an atom

atomic number

identifies a specific element; equals the number of protons in an atom of each element

radioactive isotope

an unstable atom in which the nucleus decays (breaks down) releasing particles and energy

isotope

atoms having the same numbers of protons but different numbers of neutrons

ionic bond

occurs when atoms transfer electrons to other atoms

ion

atoms that have lost or gained electrons

covalent bond

occurs when atoms share electrons

molecule

atoms that are held together by covalent bonds

chemical reaction

interaction of substances that lead to the formation of new substances

reactant

the starting materials for a reaction; found on left side of chemical equation

product

ending materials of a reaction; found on right side of chemical equation

organic compound

substance made of two or more elements, one being carbon

inorganic compound

substance made of two or more elements, none of which is carbon

valence electrons

electrons in the outermost energy level; they are involved in bond formation

single bond

a covalent bond in which one pair of electrons is shared

double bond

a covalent bond in which four valence electrons are shared between two atoms

chemical formula

indicates the number and types of atoms in a molecule

structural formula

shows the number and types of atoms in a molecule and how they are arranged

chemical reaction

indicates the formation of new substances from previous substances

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