The Bohr Model of the Hydrogen Atom
Unit 6A:  Atomic Theory (Quantum/Electronic Structure)
Knowledge/Understanding Goals:
•	developments leading to the Bohr model of the atom
•	the Bohr model and its limitations
•	how the modern quantum mechanical model of the atom grew out of the Bohr model
Skills:
•	calculate the frequency/wavelength of light emitted using the Rydberg equation
•	calculate the energy associated with a quantum number using Bohr’s equation
Significant Developments Prior to 1913
Discovery of the Electron (1897):  J.J. Thompson determined that cathode rays were actually _____________ emitted from atoms that the cathode was made of.  These particles had an ___________________, so they were named “electrons”.
	Cathode Ray Experiment: 

https://www.youtube.com/watch?v=GzMh4q-2HjM
Discovery of the Nucleus (1909):  Ernest Rutherford’s famous “_________________________” determined that atoms contained a __________, _______________-charged region that comprised most of the atom’s mass.  This region was named the “______________”, after the nucleus of a cell.
Gold Foil Experiment:

http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf
Rutherford (“Planetary”) Model of the Atom (1911):  The atom was believed to be like a miniature solar system, with electrons orbiting the nucleus in much the same way as planets orbit the sun. Electrons could be found orbiting anywhere within the low density “_______________” region.

Rydberg Formula (1888):  Johannes Rydberg developed a generalized formula that could describe the __________________ of all of the spectral lines in hydrogen (and similar elements).
There are several series of spectral lines for hydrogen, each of which converge at different wavelengths.  Rydberg described the Balmer series in terms of a pair of integers (n1 and n2, where n1 < n2), and devised a single formula with a single constant (now called the Rydberg constant) that relates them.  (RH = ___________________)

Rydberg’s equation was later found to be consistent with other series discovered later, including the Lyman series (in the ultraviolet region; first discovered in 1906) and the Paschen series (in the infrared region; first discovered in 1908).
Those series and their converging wavelengths are:
Series	Wavelength	n1	n2	
Lyman	91 nm	1	2 → ∞	
Balmer	365 nm	2	3 → ∞	
Paschen	820 nm	3	4 → ∞	

Bohr’s Model of the Atom (1913)
In 1913, Niels Bohr combined atomic, spectroscopy, and quantum theories into a single theory.  Bohr hypothesized that electrons moved around the nucleus as in Rutherford’s model, but that these electrons had only certain allowed _____________ values of ___________, which could be described by a quantum number (n).  The value of that quantum number was the same n as in Rydberg’s equation, and that using quantum numbers in Rydberg’s equation could predict the ________________ of light emitted when the electrons ______________ or __________ energy by moved from one quantum level to another.

Bohr’s model gained wide acceptance, because it related several prominent theories of the time.  The theory worked well for hydrogen, giving a theoretical basis for Rydberg’s equation.  Bohr defined the energy associated with a quantum number (n) in terms of Rydberg’s constant:

http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::800::600::/sites/dl/free/0072482621/59229/Bohr_Nav.swf::The%20Bohr%20Atom
The Bohr model worked well for hydrogen.  However, the equations could not be solved exactly for atoms with more than one electron, because of the additional effects that ___________________ exert on each other (Coulomb force ).

By the mid-1920s, quantum physics was changing.  The concept of “allowed states” gave way to __________________ distributions, governed by Werner Heisenberg’s uncertainty principle, which states that there is a limit on how much certainty can exist in the state of a sub-atomic particle.  
For example, the more exactly an electron’s _____________ is specified, the less the exactly the _____________ or momentum can be specified.
Or, as soon as you observe light energy, it loses its duality. (must act as either a ___________ or a _____________)
In 1925, Erwin Schrödinger used the “wave equation”—an equation that describes how a wave changes with time—to describe where ______________ would be found (in terms of _______________) if the electron behaved as a __________ rather than as a _______________.
Schrödinger found that by treating each electron as a unique wave function governed by the wave equation, the _______________ of the electrons could be predicted by the solutions to the wave equation without the need for an empirically-derived number (the Rydberg constant).  This use of Schrödinger’s equation to construct a _______________________ for the electrons in an atom is the basis for the modern _______________________________ of the atom.
Probability Maps: 

Each map represents a specific _________, capable of holding __ electrons. The ________ of each orbital are determined using Schrödinger’s equation.