Sorry this is late Mrs. Mills! Our internet has been down so I couldn't do my typing until the weekend. This website wouldn't let me add pictures either .... so is that points taken off for not having pictures? -Kristiana :)
Proust discovered the Law of Definite Proportions. He stated that two elements ALWAYS must remain the same.
In 1803 Dalton revealed his concepts of Dalton's Law of Partial Pressures.
Sometime in the 1800's Dalton became the first person to explain the behavior of atoms in terms of measurement of weight.
Avogadro created the Avogadro's law which stated that equal volumes of gases, with the same amount of temperature and pressure, MUST contain the same number of molecules.
Miraculously arranged 63 elements by atomic mass into a periodic table.
Thompson's discovered the electron.
Thompson also figured that e m must be composed of a single type of a negatively charged particle.
In 1898 Curie found the existence for a brand new, higher power radioactive element.
In 1902 Curie discovered the new elements Polonium and Radium.
Hans Geiger showed that in 1910 that if you take two alpha-particles then they are emitted into the radioactivity uranium.
In 1912 Geiger and Nuttal proved that it is true and it is caused by two uranium isotopes.
Ernest Rutherford came up with the fact that most of an atom is made of emptiness.
Bohr's assumptions said that if you have electrons that are traveling in orbits then they are defined by angular momentum.
Enrico Fermi invented the first nuclear reactor so that nuclear chain reactions are controlled at a nice, steady rate.