1. Important People in the Development of Atomic Theory Exam Review

2. Democritus The theory of Democritus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; 440 BC

3. Aristotle Disagreed with Democritus Only 4 elements exist- fire, water, air and earth 350 BC

4. John Dalton Father of Modern Atomic Theory (1800) Five main points of Dalton's atomic theory Elements are made of extremely small particles called atoms.atoms Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.chemical compounds In chemical reactions, atoms are combined, separated, or rearranged.chemical reactions

5. Ludwig Boltzman Developed the Kinetic Theory of Matter originally only gasses.Kinetic Theory of Matter As pointed out by Albert Einstein in 1905, this experimental evidence for kinetic theory is generally seen as having confirmed the existence of atoms and molecules.Albert Einstein 1866

6. Dmitri Mendeleev Authored 1st Periodic Table of the Elements, it contained all the elements known at the time. 1869

7. James Chadwick In 1931, Chadwick discovered the neutron. It allowed researchers to make elements heavier than uranium. For Chadwick's discovery of the neutron in 1932, he was awarded the Hughes Medal of the Royal Society in 1932 and the Nobel Prize in Physics in 1935.Hughes MedalRoyal SocietyNobel Prize in Physics