In 1803 Dalton propsed the atomic theory which states:
All matter is made of atoms and cannot be destroyed
All atoms of the same element have similar charecteristicsThere are three types of atoms: elements, compounds and molecules
Around 1802 he began to estimate the weights of some atoms, though many of his estimates were off. Dalton did establish
that when elements combine they must do so in certain fixed amounts.
Though much of what he said has been changed as the atomic theory evolved, John Dalton is essentially the father of the
modern atomic theory.