jan 1, 1913 - Neil Bohr's Atomic Theory
In 1913, Neil Bohr discovered that the electrons are fixed in circular motions around the nucleus. After experimenting, the Danish scientist stated that the circular motions are energy levels. The electrons become larger the further away they are from the nucleus and have higher energy. He also identified that an electron can jump from a lower level to a higher level by absorbing energy. This can be done in the forms of heat, light or electricity. In the picture, the different energy levels are shown.
Added to timeline:
Atomic Theory Timeline - Adrianne Moran 4th Period Chemistry