Atomic Model Vocabulary

Isotopes

Atoms of the same element that have different numbers of neutrons

law of definite proportions

States that a chemical compound will always have the same amount of each element by weight, no matter what the amount is, or source.

Law of Multiple Proportions

States that whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of a small whole number.

atomic mass unit (amu)

a mass equal to one twelfth the mass of an atom of carbon-12

cathode ray

a stream of electrons leaving the negative cathode in a discharge tube containing a gas at low pressure, or electrons emitted by a heated filament in certain electron tubes.

atomic theory

a theory that states that all matter is composed of tiny particles called atoms.

Alpha particles

positively charged particles consisting of two protons and two neutrons tightly bound together

Law of Conservation of Mass

states that in a chemical reaction mass is neither created nor destroyed

atomic mass

the amount of matter contained in an atom of an element

mass number

the total number of protons and neutrons in an atom