http://www.ck12.org Chapter 24. Atomic Physics
24.2 The Bohr Atom
Objectives
The student will:
- Understand the role that atomic spectra had in explaining the internal structure of the atom.
- Solve problems involving the Balmer series.
- Understand Bohr’s atomic theory.
- Solve problems using the equation for the Bohr atom.
Vocabulary
- balmer series:The results for emitted hydrogen spectra, given by Balmer’s equation.
- Bohr radius: The smallest orbital radius of the hydrogen atom,r 1 = 0. 529 × 10 −^10 m.
- emission spectrum:The distinct set of sharp bright lines produced when the light from a heated element is
refracted in a prism, also known as line spectrum. - ground state: The lowest-energy state of an atom.
- stationary states:A situation in which electrons are existing within specific orbits around a nucleus. An
electron in each stationary state possesses a definite energy. - transition: Electrons that have undergone a change in energy are said to have undergone a transition.
Emission Spectrum of Hydrogen
Heating different elements creates different kinds of light. This is usually done by taking the gaseous form of an
element, putting it in a sealed glass tube, and applying high voltage to the gas. The high voltage ionizes the gas
and it gives off a distinct color depending on the element. For example, neon gas glows a bright red-orange color
(the natural color of neon signs), while sodium vapor glows yellow and hydrogen glows pink. As discussed earlier,
when sunlight is refracted through a prism, we see a rainbow spectrum. When the light from a heated element is
refracted in a prism, however, we don’t see a smooth rainbow spectrum. Instead, we see a distinct set of sharp bright
lines, called theemission spectrum(orline spectrum) of that element. The diagram below shows a simple model
of a spectroscope to measure the emission spectrum of hydrogen.
In an actual spectroscope, a diffraction grating may be used instead of a triangular glass prism, but the effect is the
same –to separate colors in proportion to their wavelength. A detailed view of this is explained in the video in the
link below.