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Joseph Proust
09/26/1754 -07/05/1826
-Created Law of Definite Proportions in 1799 - The law stated that a compound is composed of exact proportions of elements by mass regardless of how the compound -
John Dalton
09/06/1766-07/27/1844
-Dalton's theory in 1803
-His theory:
-All matter is composed of atoms
-Atoms cannot be made or destroyed
-All atoms of the same element are identical
-Different elements have different types of atoms
-Chemical reactions happen when atoms are rearranged -Compunds are formed from atoms of the constituent elements -
Amedeo Avogadro
08/09/1776)-07/09/1856
-Created Avogadro's Molecular Theory 1811 -His theory states that equal volumes of gases contain equal numbers of molecules at the same temperature and pressure. -
Dmitri Mendeleev
02/08/1834-02/02/1907
In the late 1860's, Mendeleev began working on his great achievement: the periodic table of the elements.
63 elements then known by their atomic weights, he managed to organize them into groups possessing similar properties.
Theory was held to be a means of organizing data, not a description of reality. -
JJ Thomson
12/18/1856-08/30/1940
-Thomson discovered the electron in 1897
- The Properties of Electrons theory:
-Electrons travel in a straight line
-Electrons have momentum and kinetic energy -
Marie Curie
11/07/1867-07/04/1934
Worked on radioactivity and in 1898 she reported the possible existence of a new, powerfully radioactive element.
Discovered the radioactive elements polonium and radium in the pure state in 1902.
THEORY OF RADIOACTIVITY
Discovered Uranium and Thorium were also radioactive. -
Ernest Rutherford
08/30/1871-10/19/1937
-Rutherford's Gold Foil Experiment in 1910
-Rutherfords theory:
-Most of the parts of an atom are empty .
-Approximately all the mass of an atom is concentrated at the nucleus. -
Hans Geiger
09/30/1882- 09/24/1945
Invented the Geiger Counter along with Ernest Rutherford.
Counter counted alpha-particles and identified alpha-particles as the nucleus of the helium atom.
Geiger-Nuttall Rule says a linear relationship exists between longarithm of range of alpha-particles and radioactive time constant -
Niels Bohr
10/07/1885-11/18/1962
New theory on the structure of the atom in 1913
Quantum Theory
-characteristic of electrons having fixed energy quantities -
Enrico Fermi
09/29/1901-11/28/1954
Invented the Nuclear Reactor
Reactor is used in Nuclear Power Plants today
In 1933, he developed the theory of beta decay, postulating that the newly-discovered neutron decaying to a proton emits an electron and a particle which he called a "neutrino".
