Chapter 9 and 10 Atoms and Nuclear Physics

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alpha decay
The disintegration of a nucleus into a nucleus of another element with the emission of an alpha particle, which is a helium nucleus.
atomic mass
The weighed average mass of an atom of the element in naturally occurring samples; given under its symbol in the period table (in atomic mass units, symbolized u).
atomic number
Symbolized by the letter Z, it is equal to the number of protons in the nucleus of each atom of that element.
beta decay
The disintegration of a nucleus into a nucleus of another element with the emission of a beta particle, which is an electron.
carbon-14 dating
A procedure used to establish the age of ancient organic remains by measuring the amount of 14C in an ancient sample.
chain reaction
Occurs when each fission event causes at least one or more fission events.
critical mass
The minimum amount of fissionable material necessary to sustain a chain reaction.
Negatively charged subatomic particles.
A substance in which all the atoms have the same number of protons (the same atomic number, Z).
The process in which a large nucleus “splits” (fissions) into two intermediate-size nuclei, with the emission of neutrons and the conversion of mass into energy.
The process in which smaller nuclei combine to form larger ones with the release of energy.
gamma decay
An event in which a nucleus emits a gamma ray and becomes a less energetic form of the same nucleus.
The time it takes for half the nuclei in a given radioactive sample to decay.
Forms of nuclei of an element that have the same numbers of protons but differ in their numbers of neutrons.
mass defect
The decrease in mass in a nuclear reaction.
mass number
The number of protons plus neutrons in a nucleus; the total number of nucleons.
neutron number
N, the number of neutrons in the nucleus of an atom.
Neutral particles found in the nuclei of atoms.
A collective term for neutrons and protons (particles in the nucleus).
The central core of an atom; composed of protons and neutrons.
A particular species or isotope of any element, characterized by a definite atomic number and mass number.
A high-temperature gas of free electrons and positively charged ions.
Positively charged particles in the nuclei of atoms.
radioactive isotope
A nuclide whose nucleotide undergoes spontaneous decay (disintegration).
The spontaneous process of nuclei undergoing a change by the emitting particles or rays.
Types of nuclei that undergo radioactive decay.
strong nuclear force
The short-range force of attraction that acts between two nucleons and holds the nucleus together. atom The smallest particle of an element that can enter into a chemical combination.
dual nature of light
Light must be described sometimes as a wave and sometimes as a particle.
Negatively charged subatomic particles.e-= -1.6 x 10[-13]C
excited states
The energy levels above the ground state in an atom. See ground state.
ground state
The lowest energy level of an atom.
Heisenberg’s uncertainty principle
It is impossible to know a particle’s exact position and velocity simultaneously.
An acronym for light amplification by stimulated emission of radiation; it produces coherent, monochromatic light.
line absorption spectrum
A set of dark spectral lines of certain frequencies or wavelengths, formed by dispersion of light that has come from an incandescent source and has then passed through a sample of cool gas.
line emission spectrum
A set of bright spectral lines of certain frequencies or wavelengths formed by dispersion of light from a gas discharge tube. Each element gives a different set of lines.
matter (de Broglie) waves
The waves associated with moving particles.
photoelectric effect
The emission of electrons that occurs when certain metals are exposed to light.
A “particle” of electromagnetic energy.
principal quantum number
The numbers n = 1, 2, 3, . . . used to designate the various principal energy levels that an electron may occupy in a hydrogen atom.
A discrete amount of energy.
quantum mechanics
The branch of physics that replaced the classical-mechanical view (that everything moved according to exact laws of nature) with the concept of probability. Schrödinger’s equation forms the basis of quantum wave mechanics.
stimulated emission
Process in which an excited atom is caused to emit a photon.
High-frequency, high-energy electromagnetic radiation formed when high-speed electrons strike a metallic target.
Categories: Atomic Physics