Chapter 7: The Quantum-Mechanical Model of an Atom
Quantum Mechanics: The Theory That Explains the Behavior of the Absolutely Small
•Quantum-Mechanical Model: a model that explains how electrons exist in atoms and how
those electrons determine the chemical and physical properties of elements.
The Nature of Light
•Electromagnetic Radiation: a type of energy embodied in oscillating electric and magnetic
oElectric Field: a region of space where an electrically charged particle experiences a
force (proton or electron).
oMagnetic Field: a region of space where a magnetic particle experiences a force
•Light travels faster than sound that’s why we see lightning before we hear thunder.
•Amplitude: the vertical height of a crest or depth of a trough.
oThe greater the amplitude, the greater the intensity or brightness of the light.
•Wavelength ( ): the distance between adjacent crests or any two analogous points.
oThe amplitude and wavelength can vary independently of one another.
•Frequency (v): the number of cycles or wave crests that pass through a stationary point in a
given period of time (in Hertz or s-1).
oThe frequency of a wave is directly proportional to the speed at which the wave is
oFrequency is inversely proportional to the wavelength.
ov = c/
•For visible light, light that can be seen by the human eye, wavelength or frequency
oRed has the longest wavelength of visible light and violet has the shortest
oWhen a substance absorbs some colors while reflecting others, it appears colored.
oA red shirt appears red because it reflects red light while absorbing most of the other
•Electromagnetic Spectrum: all wavelengths of electromagnetic radiation.
oA short wavelength has greater energy than a long wavelength.
oLow to high energy or longer to shorter wavelength: radio, microwave, infrared,
visible light (red to violet), ultraviolet, x-ray and then gamma rays.
•Interference: waves interact with each other that cancel each other out or build each other
up, depending on their alignment upon interaction.
oConstructive Interference: if two waves of equal amplitude are in phase when they
interact, they align with overlapping crests, a wave twice the amplitude (bright line).
oDestructive Interference: if two waves of equal amplitude are completely out of phase
when they interact, they align so that the crest from one source overlaps with the
trough from the other source (dark line).