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Said solid forms of matter are composed of indivisible elements shaped like triangles -
Believed atoms were uniform, solid, hard, incompressible, and indestructible and moved in infinite numbers until stopped -
Believed all metals could be turned into other metals -
Believed everything was composed of very tiny particles -
Said matter was composed of atoms that were not created or destroyed during chemical reactions -
Proposed his atomic theory and proposed that all matter is made of atoms -
Found that the volumes of gas contain equal numbers of molecules -
Made the early version of the periodic table with the 70 known elements -
Discovered the strongly radioactive elements polonium and radium -
Proved the existence of atoms mathematically -
His work proved electrons have a fixed, measurable charge that does not vary -
Described the atom as having a tiny, dense, and positively charged core called the nucleus -
Proposed a theory for the hydrogen atom and said some physical quantities only take discrete values -
Found that the frequency of x-ray radiation has a precise relationship to an element's atomic number -
Developed a mathematical way to express the energy levels of electrons in atoms -
Created the electron cloud model -
Found that the atoms consisted of protons and electrons and another subatomic particle called the neutron -
Proposed that all atoms contain tiny negatively charged subatomic particles or electrons