Ch 21 Nuclear

Activity

Reactivity

Radioactivity

The spontaneous emission of radiation by an unstable atomic nucleus

Alpha particle

A helium nucleus emitted by a radioactive substance.

Alpha decay

A nuclear reaction in which an atom emits an alpha particle consisting of two protons and two neutrons.

Atomic number

The number of protons in the nucleus of an atom.

Beta particle

A high-speed electron that is emitted during radioactive decay.

Beta decay

Radioactive decay in which an electron is emitted from the nucleus.

Belt of Stability

A line representing stable atomic nuclei that appears when the number of neutrons versus the number of protons in isotopes is graphed.

Electron capture

The process in which an inner orbital electron is captured by the nucleus of the atom that contains the electron.

Fission

A nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy.

Fusion

Creation of energy by combining two small nuclei into one.

Gamma emission

a radioactive decay process in which high-energy, short-wavelength photons are given off

Half-life

Length of time required for half of the radioactive atoms in a sample to decay

Isotopes

Atoms of the same element that have different numbers of neutrons

Kinetics

The study of reaction rates

Nuclear reaction

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

Nuclear transmutation

Nuclear reaction that results from the bombardment of nuclei by neutrons, protons, or other nuclei

Mass defect

The difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons

Nuclear binding energy

The energy released when a nucleus is formed from nucleons

Mass number (atom)

Atom - The sum of the number of neutrons and protons in an atomic nucleus

Mass number (element)

Weighted average of the mass numbers of the isotopes

Nucleus

The center of an atom, containing the protons and neutrons

Nuclide

A general term for a specific isotope of an element

Nucleon

A proton or neutron

Neutron

A subatomic particle that has no charge and that is found in the nucleus of an atom

Proton

A subatomic particle that has a positive charge and that is found in the nucleus of an atom

Positron

A particle with the mass of an electron but a positive charge

Positron emission

A radioactive decay process in which a proton in the nucleus is converted into a neutron and a positron and then the positron is emitted from the nucleus

Radioactive decay

A radioactive isotope breaks down into a more stable isotope.

Radiometric dating

Method used to determine the age of rocks using the rate of decay of radioactive isotopes

Radiocarbon dating

Method for determining age by comparing the amount of carbon-14 to the amount of carbon-12 in a sample

Radionuclides

Radioactive isotopes

Radiotracers

Isotopes injected into patients and detected by camera; image analyzed by computer; shows size, shape, and activity of organs and cells

Radon

A radioactive noble gas that arises from the earth's crust