Niels Bohr and a New Picture of the Atom

A glowing tube of hydrogen gas can reveal something surprising about atoms. Pass its light through a prism, and the glow separates into distinct colored lines rather than a continuous rainbow. In the early 1900s, scientists knew about these lines, but explaining why they appeared at particular colors was a challenge. Danish physicist Niels Bohr proposed an answer that changed the picture of the atom.

A puzzle inside the atom

Bohr was born in Copenhagen, Denmark, on October 7, 1885. He studied physics at the University of Copenhagen and later worked in England, where scientists were investigating the structure of atoms. Atoms were already known to contain electrons, tiny particles with negative electric charge. But scientists were still debating how those electrons were arranged.

In 1911, physicist Ernest Rutherford proposed that an atom has a small, dense, positively charged center called the nucleus. His model grew out of experiments in which a beam of particles was directed at thin gold foil. Most particles passed through, but a few were deflected sharply. Those results suggested that most of an atom is empty space, with much of its mass concentrated in the nucleus.