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Unit 3: Atoms and Light—Exploring Atomic and Electronic Structure

Glossary

Alpha particle
A product of nuclear decay that is two protons and two neutrons, which form a particle with a structure identical to that of a helium nucleus with a charge of +2.
Blackbody radiation
A type of electromagnetic radiation that is emitted by a black body (a nonreflective and opaque object at uniform and constant temperature), such as the light emitted by a glowing hot stove coil.
Cathode ray tube
An evacuated tube with two electrodes inside it. High voltage electricity is applied to the negative electrode, creating a stream of electrons that travel to the positive electrode.
Decay
Occurs when the nucleus of an unstable atom disintegrates, emitting radiation (such as alpha particles, beta particles, or positrons) causing the atom to lose energy and become a different isotope.
Electromagnetic radiation
Radiation that is emitted and moves in a wave-like shape. It is synonymous with the word "light."
Electrons
Negatively charged subatomic particles.
Inertia
The measure of an object's reluctance to accelerate under an applied force.
Infrared
A form of electromagnetic radiation that falls between the visible light and microwave areas of the electromagnetic spectrum. Infrared light is further divided into "far," "mid," and "near" regions. Far infrared light is thermal, and we experience it as heat. Near infrared waves are used in fiber optic telecommunications.
Inversely proportional
Two variables are inversely proportional to each other if as the value of one variable increases, the value of another variable decreases at the same rate.
Neutron
A subatomic particle with no net electric charge that combines with protons to form the nucleus of the atom. The number of neutrons in an atom determines the isotope of the element.
Nucleus
The core of the atom, which consists of protons and neutrons. The diameter of the nucleus is extremely small relative to the diameter of the entire atom, which includes its electron cloud. The number of protons in the nucleus determines which element the atom is.
Photoelectric effect
The name given to what happens when light shines on the surface of an element, and then electrons are emitted from it, usually in the form of electricity.
Photon
An elementary particle (a particle lacking substituent parts) and the quantum (smallest unit) of electromagnetic radiation (light).
Proton
A positively charged subatomic particle that combines with neutrons to form the nucleus of the atom. The number of protons in the nucleus uniquely determines which specific element that atom is.
Quantum model of the atom
A model of the atom that describes the electrons in the atom as having only very specific values of energy and locations in space.
Schrödinger equation
A differential equation that, when solved for an atom, gives many possible solutions, corresponding to different possible wave functions for that atom. This equation is important in quantum mechanics because it demonstrates that an atomic orbital can be described as a probability distribution map of the position of an electron (rather than a rigidly defined orbital, in which the location of an electron can be known).
Spectroscopy
The study of light being absorbed or emitted by matter.
Speed of light
The speed of light in vacuum is 299,799,458 meters per second, and is the maximum speed any energy or matter can travel.
Subatomic particles
The particles into which an atom can be split.
Ultraviolet
A form of electromagnetic radiation that falls between X-rays and visible light. Ultraviolet radiation from the sun is filtered through the Earth's atmosphere, mitigating its harmful effects on human health, yet the small fraction that penetrates the atmosphere can cause skin damage and cancer.
Wave particle duality
In quantum mechanics, when fast moving particles of matter or photons of energy blur the lines between the wave-like nature of light and the particle-like nature of an object.
Wavefunction
In the solutions to the Schrödinger equation, electrons can be associated with mathematical functions, called "wavefunctions," that relate to their energy and probable locations in space.

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