Matter and Chemical Reactions Vocab

Atom

building block of matter; contains subatomic particles—neutrons, protons, and electrons

Nucleus

the center of an atom; contains neutrons and protons

Proton

a positively charged particle in an atom’s nucleus

Neutron

a particle without charge in an atom’s nucleus

Electron

a negatively charged particle that occupies space around an atom nucleus

Element

a pure substance composed of only one type of atom; cannot be broken down into another substance by physical or chemical means

Isotope

two or more atoms of the same element having different numbers of neutrons

Compound

a pure substance with unique properties, formed when two or more different elements combine

Covalent bond

a type of chemical bond formed when atoms share electrons

Molecule

a compound whose atoms are held together by covalent bonds

Ion

an atom that is positively or negatively charged because it has lost or gained electrons

Ionic bond

an electrical attraction between two oppositely charged atoms or groups of atoms

Chemical reaction

energy-requiring process by which atoms or groups of atoms in substances are changed into different substances

Reactant

substance that exists before a chemical reaction; located on the left side of the arrow in a chemical equation

Product

substance formed by a chemical reaction; located on the right side of the arrow in a chemical equation

Activation energy

minimum amount of energy needed for reactants to form products in a chemical reaction

Catalyst

substance that speeds up a chemical reaction by reducing the activation energy but is not itself consumed in the reaction

Enzyme

protein that speeds up a biological reaction by lowering the activation energy needed to start the reaction; a biological catalyst

Active site

the specific place where a substrate binds on an enzyme