Chapter 9:Atomic Physics

atom

The smallest particle of an element that can enter into a chemical combination.

electrons

Negatively charged subatomic particles found outside of the nucleus of an atom

quantum

A discrete amount of energy.

photoelectric effect

The emission of electrons that occurs when certain metals are exposed to light.

photon

A “particle” of electromagnetic energy.

dual nature of light

Light must be described sometimes as a wave and sometimes as a particle.

line emission spectrum

A set of bright spectral lines of certain frequencies or wavelengths formed by dispersed light from a gas of a heated element. Each element gives a different set of lines.

line absorption spectrum

A set of dark spectral lines of certain frequencies or wavelengths, formed by the absorption of dispersed light that has passed through a sample of cool gas.

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.

ground state

The lowest hydrogen atom energy level, n=1 .

excited states

The energy levels above the ground state in an atom.

x-rays

High-frequency, high-energy electromagnetic radiation formed when high-speed electrons strike a metallic target

laser

An acronym for light amplification by stimulated emission of radiation; it produces coherent, monochromatic light.

stimulated emission

Process in which an excited atom is caused to emit a photon.

heisenberg’s uncertainty principle

It is impossible to know a particle’s exact position and velocity simultaneously.

matter (de Broglie) waves

The waves associated with moving particles.

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.