Chap 4 chemistry

radioactivity

The process in which some substances spontaneously emit radiation.

atom

(physics and chemistry) the smallest component of an element having the chemical properties of the element

atomic mass unit

1/12 the mass of a carbon-12 atom

alpha particle

A cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of radioactivity

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.

Neutrons

A neutral subatomic particle in an atom's nucleus that has a mass nearly equal to that of a proton.

cathode ray

A ray of radiation that originates from the cathode and travels to the anode of a cathode ray tube.

Nuclear reaction

A reaction that involves a change in the nucleus of an atom.

radioactive decay

A spontaneous process in which unstable nuclei lose energy by emitting radiation.

proton

A subatomic particle in an atom's nucleus that has a positive charge of 1 +.

Nuclear equation

A type of equation that shows the atomic number and mass number of the particles involved.

isotope

Atoms of the same element with the same number of protons but different numbers of neutrons

Gamma ray

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.

atomic number

Number of protons in an atom

alpha radiation

Particles repelled by a positively charged electrode, attached by a negatively charged electrode., 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

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.

nucleus

The extremely small, positively charged, dense center of an atom that contains positively charged protons, neutral neutrons, and is surrounded by empty space through which one or more negatively charged electrons move.

mass number

The number after an element's name, representing the sum of its protons and neutrons.

radiation

The rays and particles-alpha and beta particles and gamma rays--that are emitted by radioactive materials.

beta particle

a high speed electron with a 1 charge that is emitted during radioactive decay

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.

atomic mass

the weighted average mass of the isotopes of that element