5 Steps to a 5 AP Chemistry

 137

Spectroscopy, Light, and Electrons

IN THIS CHAPTER

Summary:In developing the model of the atom it was thought initially that

all subatomic particles obeyed the laws of classical physics—that is, they

were tiny bits of matter behaving like macroscopic pieces of matter. Later,

however, it was discovered that this particle view of the atom could not

explain many of the observations being made. About this time the dual

particle/wave model of matter began to gain favor. It was discovered that in

many cases, especially when dealing with the behavior of electrons, describ-

ing some of their behavior in terms of waves explained the observations

much better. Thus, the quantum mechanical model of the atom was born.

Keywords and Equations

Speed of light, c=3.0× 108 ms−^1

E=energy n=frequency l=wavelength

p=momentum v=velocity n=principal quantum number

m=mass E= hn c=ln p=mv

En=

Planck’s constant, h=6.63× 10 −^34 Js

The Nature of Light

Light is a part of the electromagnetic spectrum—radiant energy composed of gamma rays,

X-rays, ultraviolet light, visible light, etc. Figure 10.1 shows the electromagnetic spectrum.

−×2.178 10−

joule

18

n^2

λ=

h

mv

CHAPTER

10

KEY IDEA