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Chemistry Ch.4

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Alpha Particle
a particle with two protons and two neutrons, has a 2+ charge, is equivalent to a helium-4 nucleus. Is emitted during radioactive decay.
Alpha Radiation
radiation that is made up of alpha particles; is deflected toward a negatively charged plate when radiation from a radioactive source is directed between two electrically charged plates
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 (amu)
one-twelfth the mass of a carbon-12 atom
Atomic Number
the number of protons/electrons in an atom
Beta Particle
a high-speed electron with a 1- charge that is emitted during radioactive decay
Beta Radiation
radiation that is made up of beta particles; is deflected toward a positively charged plate when radiation from a radioactive source is directed between two electrically charged plates
Cathode Ray
radiation that originates from the cathode and travels to the anode of a cathode-ray tube
Electron
a negatively charged, fast-moving particle with an extremely small mass that is found in all forms of matter and moves through the empty space surrounding an atom's nucleus
Element
a pure substance that cannot be broken down into simpler substances by physical or chemical means
Gamma Rays
high-energy radiation that has no electrical charge and no mass, is not deflected by electric or magnetic fields, usually accompanies alpha and beta radiation, and accounts for most of the energy lost during radioactive decay
Isotopes
atoms of the same element with different numbers of neutrons
Mass Number
the number after an element's name, representing the sum of its protons and neutrons
Model
a visual, verbal, and/or mathematical explanation of data collected from many experiments
Neutron
a neutral, subatomic particle in an atom's nucleus that has a mass nearly equal to that of a proton
Nuclear Equation
a type of equation that shows the atomic number and mass number of the particles involved
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 positively charged protons and neutral neutrons
Periodic Table
a chart that organizes all known elements into a grid of horizontal rows (periods) and vertical columns (groups or families) arranged by increasing atomic number
Proton
a subatomic particle in an atom's nucleus that has a positive charge of 1+
Radiation
the rays and particles - alpha and beta particles and gamma rays - that are emitted by radioactive materials
Radioactive Decay
a spontaneous process in which unstable nuclei lose energy by emitting radiation
Radioactivity
the process in which some substances spontaneously emit radiation
Theory
an explanation supported by many experiments; is still subject to new experimental data, can be modified, and is considered valid if it can be used to make predictions that are proven true