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Chapter 4 Vocabulary

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alpha particles
a particle with two protons and two neutrons with a 2+ charge
alpha radiation
radiation that is made up of alpha particles
atom
the smallest particle of an element that retains all the properties of that element
atomic mass
the weighted average mass of the isotopes of that element
atomic mass unit
one twelfth the mass of a carbon- 12 atom
atomic number
the number of protons in an atom
beta particles
a high-speed electron with a 1- charge that is emitted during radioactive decay
beta radiation
radiation made up of beta particles
cathode ray
a ray of radiation that originates from the cathode and travels to the anode of a cathode ray tube
Dalton's atomic theory
a theory proposed by John Dalton in 1808, based on numerous scientific experiments that marked the beginning of the development of modern atomic theory
electron
a negatively charged, fast-moving particle with an extremely small mass
gamma ray
high-energy radiation that has no electrical charge and no mass, it is not deflected by electric or magnetic fields, usually accompanies, alpha and beta radiation
isotopes
atoms of the same element with the same number of protons but different numbers of neutrons
mass number
the number after an element's name representing the sum of its protons and neutrons
neutron
a neutral subatomic particle in an atom's nucleus that has a mass nearly equal to that a person
nuclear equation
a type of equation that shows atomic number and mass number of the particles involve
nuclear reaction
a reaction that involves a change in the nucleus of an atom
nucleus
the extremely small, positively charged, dense center of an atom that contains protons
proton
a subatomic particle in an atom's nucleus that has a positive charge of 1+
radiation
the rays and particles (alpha, beta, gamma) that are emitted by radioactive materials
radioactive decay
a spontaneous process in which unstable nucleus lose energy by emitting radiation
radioactivity
the process in which some substances spontaneously emit radiation
mole
the SI unit used to measure the amount of a substance (atom)
molar mass
the mass in grams of one mole of any pure substance