http://www.ck12.org Chapter 5. Electrons in Atoms
5.1 Light
Lesson Objectives
- Describe the relationships between speed, wavelength, and frequency of light.
- Understand the photoelectric effect and how it is related to the wave-particle duality of light.
- Describe how changes in electron energies lead to atomic emission spectra.
- Describe the Bohr model of the atom.
Lesson Vocabulary
- atomic emission spectrum
- electromagnetic radiation
- electromagnetic spectrum
- excited state
- frequency
- ground state
- photoelectric effect
- photon
- quantum
- wavelength
Properties of Light
The nuclear atomic model proposed by Rutherford was a great improvement over previous models, but it was still
not complete. It did not fully explain the location and behavior of the electrons in the vast space outside of the
nucleus. For example, it was well known that oppositely charged particles attract one another. Rutherford’s model
did not explain why the electrons don’t simply move toward, and eventually collide with the nucleus. A number of
experiments were conducted in the early twentieth century that focused on the ability of matter to absorb and emit
light. These studies showed that certain phenomena associated with light revealed a great deal about the nature of
matter, energy, and atomic structure.
Wave Nature of Light
In order to begin to understand the nature of the electron, we first need to look at the properties of light. Prior
to 1900, scientists thought light behaved solely as a wave. As we will see later, this began to change as new
experiments demonstrated that light also has some of the characteristics of a particle. First, we will examine the
wavelike properties of light.