Periodic Table & Atoms Vocabulary

atom

• The smallest unit of a chemical element, consisting of protons, neutrons, and electrons.

• A type of molecule that contains two or more atoms bonded together.

• A particle that is smaller than an atom and does not have a nucleus.

• A form of energy that can be converted into matter.

atomic mass

• The sum of the protons and neutrons in an atom

• The total number of electrons in an atom

• The average mass of all isotopes of an element

• The mass of an atom's nucleus only

element

• Substance in which all the atoms in a sample are alike

• A mixture of different substances

• A compound made of two or more elements

• A solution that contains dissolved particles

electron cloud (Quantum Mechanics)

• Electrons follow fixed orbits around the nucleus.

• Electrons tend to occur more frequently in energy levels around the nucleus at any given time.

• Electrons are stationary and do not move around the nucleus.

• Electrons are found only in the outermost shell of an atom.

chemical formula

• Indicates the physical state of a substance

• Describes the color of a compound

• Tells which elements are in a compound and their ratios

• Represents the molecular weight of a compound

density

• Mass per unit of volume of a material

• Weight per unit of area of a material

• Volume per unit of mass of a material

• Density is the measure of temperature of a material

valence electrons

• Electrons in the outermost energy level of an atom that determine its chemical properties

• Electrons that are found in the nucleus of an atom

• Electrons that are involved in the formation of isotopes

• Electrons that are always present in the inner energy levels of an atom

atomic number

• Number of protons in the nucleus

• Number of neutrons in the nucleus

• Total number of electrons in an atom

• Mass number of the atom

chemical symbol

• A representation of a chemical reaction

• An abbreviated way to write an element’s name

• A type of chemical bond

• A measurement of atomic mass

compound

• A substance made of two or more elements that are chemically combined

• A mixture of different substances that retain their individual properties

• A single element in its pure form

• A solution where one substance is dissolved in another