Lewis began measuring the free energy values related to several chemical processes, both organic and inorganic. In 1916, he also proposed his theory of bonding and added information about electrons in the Periodic Table of Elements. His theory was that there are eight electrons in the outer orbit of an atom. He used dots to represent electrons. In 1933, he started his research on isotope separation.
Isotopes are different in weight from single elements.
Lewis worked with isotope of hydrogen and managed to prepare pure water containing isotope hydrogen. Lewis also was successful with acid and base chemical bonding theory. During the last years of his life he also did some photochemistry, which is the interaction of light energy with chemical compounds to create a reaction. Lewis was a very young and brilliant chemist. He carried out significant work on the field of chemistry.