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 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.

SCIENCE is steadily becoming severely specialised. The proportion of amateurs (in the restricted sense of the word) among original workers of all ranks decreases slowly but surely. The average ...