Greek philosopher who believed matter was discontinuous and called the indivisible particles of matter "atoms"
Greek philosopher who believed matter was continuous and composed of four elements - fire, earth, water, and air; also believed matter could be hot, cold, wet, or dry
proposed all matter is made up of individual particles called atoms which cannot be divided; believed all atoms of the same element have the same and mass and vice versa; believed compounds contain atoms of more than one element and atoms of different elements always combine the the same ratio in a particular compound
Joseph John Thomson
used electric current to learn more about atoms and discovered protons, neutrons, and electrons
discovered that positive charge is not evenly scattered throughout an atom and all positive charge is concentrated in its nucleus