5.1. Light http://www.ck12.org
Bohr’s model was a tremendous success in explaining the spectrum of the hydrogen atom. Unfortunately, when the
mathematics of the model was applied to atoms with more than one electron, it was not able to correctly predict
the frequencies of the spectral lines. Bohr’s model and the concept of electron transitions between energy levels
represented a great advancement in the atomic model, but improvements were still needed in order to fully understand
all atoms and their chemical behavior.
Lesson Summary
- Visible light is one part of the electromagnetic spectrum, and its wave nature can be described by its wave-
length and frequency. - The particle nature of light is illustrated by the photoelectric effect and atomic emission spectra.
- Quantum theory states that the electrons of an atom can only exist at discrete energy levels. When electrons
transition from a high energy level to a low energy level, energy is released as electromagnetic radiation. - In the Bohr model of the atom, electrons are only allowed to exist in certain orbits, each of which has a specific
distance from the nucleus and a characteristic energy level.
Lesson Review Questions
Reviewing Concept
- Answer the following:
a. List five examples of electromagnetic radiation.
b. What is the speed of all forms of electromagnetic radiations?
c. List the colors of the visible spectrum in order from shortest to longest wavelength. - Answer the following:
a. How are the wavelength and frequency of light related?
b. How are the energy and frequency of light related?
c. How are the energy and wavelength of light related? - Consider the following regions of the electromagnetic spectrum: (i) x-ray, (ii) infrared, (iii) microwave, (iv)
visible, (v) radio wave, (vi) gamma ray, (vii) ultraviolet.
a. Arrange them in order of increasing wavelength.
b. Arrange them in order of increasing energy. - Answer the following:
a. What is a quantum of energy?
b. Explain how the stacking of poker chips is related to quantum theory. - What happens when a hydrogen atom absorbs a quantum of energy? Use the terms ground state and excited
state in your answer. - Explain the difference between a continuous spectrum and an atomic emission spectrum.
- Answer the following:
a. What is the photoelectric effect?
b. Why does the photoelectric effect support the idea that light can behave as a particle? - Where are electrons located according to the Bohr model?
- Use the Bohr model to explain how the atomic emission spectrum of hydrogen is produced.
- Answer the following: