Structure of Matter Unit Vocabulary

Atomic number The number of protons in an atom’s nucleus

Chemical symbol A shorthand way to write the name of an element. Example: Ag = Gold

Electron Negatively charged particles that move around the nucleus of an atom.

Isotope Atoms of the same element that have different numbers of neutrons Example: Boron – 10 and Boron - 11

Neutron Atomic particle with no charge, neutral, that is part of an atoms nucleus

Mass number Sum of the numbers of the protons and neutrons in an atom’s nucleus

Periodic table A chart of elements arranged according to repeated changes in properties

Proton Atomic particle with a positive charge that is part of an atom’s nucleus

Quark 6 small particles that make up a neutron and proton

Boiling point The temperature at which vapor bubbles from in a liquid form to rise to the surface, increasing evaporation

Density Describes how tightly packed a substance’s molecules are

Density formula The mass per unit volume of a material D=M/V D=density M=mass V=volume

Ion A positively or negatively charged atom

Nonpolar molecule A molecule that does not have oppositely charged ends

Toxic Hazardous substance that can injure living tissues

Chemical formula A precise statement that tells which elements are in a compound and their ratios

Chemically stable Describes an atom whose outer energy level is completely filled with electrons

Corrosive Hazardous compound that attacks and alters metals, human tissue or other materials

Covalent bond A type of chemical bond formed by atoms when they share electrons, producing molecules

Chemical bond The force that holds together the atoms in a compound, occurs because atoms of most elements become more stable by gaining, losing and sharing electrons