7.S.I.3

Start of modern chemistry Lavoisier and oxygen: the idea that matter is not gained or lost in chemical reactions John Dalton revives the theory of the atom. Mendeleev develops the Periodic Table, showing that the properties of atoms of elements come in repeating (periodic) groups. Niels Bohr develops a model of the atom in shells that hold a certain number of electrons. Bohr’s model, plus the discovery of neutrons, helped e