Atomic Bonding
Year of Discovery: 1913
What Is It? The first working theory of how electrons gain, lose, and hold energy and how they orbit the nucleus of an atom.
Who Discovered It? Niels Bohr
Why Is This One of the 100 Greatest?
Marie Curie opened the century by proving that there was a subatomic world. Einstein,
Dirac, Heisenberg, Born, Rutherford, and others provided the new theoretical descriptions
of this subatomic world. But proving what lurked within an atom’s shell, and what governed its behavior, lingered as the great physics challenges of the early twentieth century.
It was Niels Bohr who discovered the first concrete model of the electrons surrounding
an atom’s nucleus—their placement, motion, radiation patterns, and energy transfers.
Bohr’s theory solved a number of inconsistencies and flaws that had existed in previous attempts to guess at the structure and activity of electrons. He combined direct experiment
with advanced theory to create an understanding of electrons. It was an essential step in
science’s march into the nuclear age.
How Was It Discovered?
Niels Bohr was only 26 in 1912—very young to step into the middle of a heated physics controversy. But that spring, as a new physics professor at the University of Copenhagen, Bohr realized atomic theory no longer matched the growing body of experimental
atomic data. One of Bohr’s experiments showed that classical theories predicted that an orbiting electron would continuously lose energy and slowly spiral into the nucleus. The atom
would collapse and implode. But that didn’t happen. Atoms were amazingly stable. Something was wrong with the existing theories—and Bohr said so.
There was no way to actually see an atom, no way to peer inside and directly observe
what was going on. Scientists had to grope in the dark for their theories, sifting through indirect clues for shreds of insight into the bizarre workings of atoms.
Atomic experimenters were building mountains of data. They recorded the particles
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