5.2. The Bohr and Quantum Mechanical Models of the Atom http://www.ck12.org
FIGURE 5.8
Electrons exist in atoms as standing
waves.Lesson Summary
- The emission spectrum of hydrogen is discontinuous. The spectrum is made up of discrete lines representing
transitions of the hydrogen electron between specific energy levels within the atom. - In 1915, Bohr proposed a new model of the atom in which electrons exist in states of constant energy, called
stationary states, orbiting at fixed distances from the nucleus. Bohr’s work was primarily based on the emission
spectrum of hydrogen. - de Broglie proposed in 1924 that any object exhibits a wavelength that is inversely proportional to its momen-
tum. Because of this relationship, only very tiny particles will exhibit measurable wavelengths. - Two years after de Broglie’s work, in 1926, the Austrian physicist Erwin Schr ̈dinger described the behavior
of electrons in atoms as standing waves. - Heisenberg showed that it is impossible to determine simultaneously both the exact location and exact velocity
of an electron or any other particle. This became known as the Heisenberg uncertainty principle.
Lesson Review Questions
- Describe the Bohr model of the hydrogen atom. What were the shortcomings of this model?
- What are emission spectra?
- Hydrogen has four, distinct emission spectra. What does general property of emissions does this indicate?
- How are emission spectra related to energy levels within an atom?
- What important property of electrons did de Broglie’s experiments demonstrate?
- What is indicated by the the term, "wave-particle duality"?
- What are the distinguishing characteristics of wave and particle behavior?
- Describe the Heisenberg uncertainty principle.