Untitled - Kelly Walsh High School

108 CHEMISTRY FOR THE UTTERLY CONFUSED
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Our goal for this chapter is to help you to learn about electrons and the current
models for where those electrons are located within the atom. You may want to
briefly review Chapter 2 concerning electrons, proton, and neutrons. Your text
will probably have some nice pictures of orbitals, so when you get to the section
on quantum numbers and orbitals, you might want to have your text handy. And
don’t forget to Practice, Practice, Practice.
7-1 Light and Matter
In the early development of the atomic model scientists initially thought that,
they could define the sub-atomic particles by the laws of classical physics—that
is, they were tiny bits of matter. However, they later discovered that this particle
view of the atom could not explain many of the observations that scientists
were making. About this time, a model (the quantum mechanical model) that
attributed the properties of both matter and waves to particles began to gain
favor. This model described the behavior of electrons in terms of waves (electromagnetic
radiation).
Light, radiant energy, makes up the electromagnetic spectrum. Light includes
gamma rays, x-rays, ultraviolet, visible, and so on. The energy of the electromagnetic
spectrum moves through space as waves that have three associated
properties: frequency, wavelength, and amplitude. The frequency, , is the number
of waves that pass a point per second. Wavelength, , is the distance
between two identical points on a wave, while amplitude is the height of the
wave. (See your textbook for a wave diagram.)
We define the energy associated with a certain frequency of light by the equation:
E h where h is Planck’s constant 6.63 10 34 Js
In the development of the quantum mechanical model of the atom, scientists
found that an electron in an atom could have only certain distinct quantities of
energy associated with it and that in order to change its energy it had to absorb
or emit a certain distinct amount of energy. The energy that the atom emits or
absorbs is really the difference in the two energy states and we can calculate it
by the equation:
E h