132 Atomic Bonding
As Bohr began to organize his teaching in 1913, he read about two new experimental
studies. First, Enrico Fermi found that atoms always emitted energy in the same few
amounts (or bursts) of energy. He called these bursts discrete quanta (quantities) of energy.
Second, chemists had studied the amount of energy that each element’s atoms radiated. They found that if they passed this radiation through a prism, the radiation was not
continuous over the whole frequency spectrum, but came in sharp spikes at certain discrete
frequencies. Different elements showed different characteristic patterns in these energy
spikes. Neither study fit with existing theories.
Bohr studied and compared these different, and apparently unrelated, bits of data,
knowing that the new data had to relate somehow—since they dealt with characteristics and
emissions from the same source: atoms.
Bohr sifted and resifted the data and the theories over an eight-month period, searching
for a way to make the experimental data fit with some atomic theory. By late that year he
had discovered a revolutionary idea: Electrons must not be as free to roam as previously
thought.
He theorized that the electrons circling an atom’s nucleus could only exist in certain,
discrete, fixed orbits. In order to jump to a closer orbit, an electron would have to give off a
fixed amount of energy (the observed spikes and quanta of radiated energy). If an electron
were to jump into a higher orbit, it would have to absorb a fixed quanta of energy. Electrons
couldn’t go wherever they wanted or carry any amount of energy. Electrons must be in one
or another of these few specific orbits. Electrons must gain and lose energy in specific
quanta.
Bohr’s atomic model was a revolutionary idea and a complete departure from previous
ideas. However, it fit well with experimental observations and explained all of the inconsistencies of previous theories. This model also explained how and why chemical elements
bonded with each other as they did.
Bohr’s discovery received instant acclaim and acceptance. For 50 years it served as the
accepted model of an atom and of the motion of electrons within the atom.
Fun Facts: Niels Bohr worked at the secret Los Alamos laboratory in
New Mexico, on the Manhattan Project (the code name for the effort to
develop atomic bombs for the United States during World War II).
More to Explore
Aserud, Finn. Redirecting Science: Niels Bohr and the Rise of Nuclear Physics. London: Cambridge University Press, 1990.
Blaedel, Niels. Harmony and Unity: The Life of Niels Bohr. Chicago: Science Technology Publishing, 1988.
Moore, Ruth. Niels Bohr: The Man, His Science, and the World They Changed. Cambridge, MA: MIT Press, 1985.
Murdoch, D. R. Niels Bohr’s Philosophy of Physics. London: Cambridge University
Press, 1999.
Rozental, S. Niels Bohr: His Life and Work. New York: John Wiley & Sons, 1997.