Thus when an atom absorbs or gives off energy (as in ... of light emitted by real hydrogen atoms. Bohr's theory that electrons existed in set orbits around the nucleus was the key to the periodic ...

Bohr applied it to the spectrum of light emitted and absorbed by hydrogen atoms. The basic hydrogen atom is the simplest of all atoms, now known to consist of a single proton and a single electron.

Bohr began to work on the problem of the atom's structure. Ernest Rutherford had recently suggested the atom had a miniature, dense nucleus surrounded by a cloud of nearly weightless electrons.

Thus when an atom absorbs or gives off energy (as in ... of light emitted by real hydrogen atoms. Bohr's theory that electrons existed in set orbits around the nucleus was the key to the periodic ...