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Antoine Lavoisier
He proved the law of conservation of mass, dicovered the element oxygen. -
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Joseph Proust
He proved the idea that every pure chemical compound consists of elements in a definite proportion.His second major advancement was giving results of his chemical analyses in terms of percentage weights. -
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John Dalton
He made an atomic theory that said all matter consists of tiny particles, Atoms are indestructible and unchangeable, Elements are characterized by the mass of their atoms, When elements react, their atoms combine in simple, whole-number ratios, When elements react, their atoms sometimes combine in more than one simple, whole-number ratio. -
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Robert Millikan
He measured the charge on an electron -
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Henri Becquerel
He discovered radioactivity on accident by leaving his sample of uranium in a closed drawer along with the photographic plate. When the weather had cleared, he returned to the drawer to retrieve his gear. He was surprised to find that the crystal had left a clear, strong image on the photographic plate. -
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JJ Thomson
He created the electron and came up with the plum pudding mocel. -
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Marie and Pierre Curie
Experimenting with their own uranium-containing ore, they came up with the term "radioactivity" to describe the spontaneous emissions that they studied. They found that the ore was significantly more radioactive than the pure material. They concluded that the ore contained additional radioactive components besides the uranium. This observation led to the discovery of two new radioactive elements which they named polonium and radium. -
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Ernest Rutherford
He bombarded gold foil with particles (alpha particles) from a radioactive source, led to the understanding of the atom. What he noted was that although most of the particles passed right through the gold foil, a very small percentage (approximately 1 in 8000) would "bounce back". He also created the planetary model of the atom -
James Chadwick
He, with help, discovered the proton. He realized the atomic number was less than the atomic mass and that the neutron did exist, and that its mass was about 0.1 percent more than the proton's.