John Dalton published his findings on atomic weights and his atomic theory in 1808 in A New System of Chemical Philosophy.
The book also included a set of symbols for the elements to help explain his findings.
In 1814, Swedish chemist Jons Berzelius improved on Dalton’s findings.
He made some of the atomic weights more accurate and supplied the weights for new elements that had been found.
Berzelius also replaced Dalton’s symbols with the initial letter of each element’s Latin name.
Oxygen became O, hydrogen H, carbon C, and nitrogen N.
Water was H2O.