Bohr

Niels Bohr was a Danish physicist who developed a model of the atom in the early 20th century. He proposed that electrons orbit the nucleus at specific distances, or "shells," and can move between these shells by absorbing or releasing energy, which explains atomic spectra. His model helped clarify how atoms behave and laid the groundwork for modern quantum mechanics, although later more complex models have been developed. Bohr’s work was fundamental in understanding atomic structure and quantum theory, influencing fields like chemistry, physics, and spectroscopy.