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1669
Hennig Brand invented the Philosopher's Stone, which could turn metals into pure gold. He also discovered phosphorus. -
1680
Robert Boyle also discovered phosphorus without knowing about Hennig Brand's discovery. -
1809
About 47 elements had been discovered and named. Scientists began to see patterns in their atom structures. -
1863
John Newlands organized the 56 then known elements into eleven separate groups based upon their atom structure. -
1869
Dimitri Mendellev used John Newlands' grouping and organized the elements into what is now known as the periodic table. He used the atomic mass as the primary characteristic to decide where each element belonged in his table. The elements were arranged in rows and columns. He even left spaces for elements to be discovered because of the pattern he saw once he started organizing those elements known at that that time -
1886
Antoine Becquerel discovered radioactivity. -
1886
Ernest Rutherford named three types of radiation: alpha and beta and gamma rays. -
1886
Pierre and Marie Curie began their work and discovered radium and polonium. They also discovered that beta particles were negatively charged -
1894
Sir William Ramsay and Lord Rayleigh discovered the noble gases and they were added to the periodic table as group O. -
1897
J. J. Thomson discovered electrons which were small negatively charged particles. -
1897
John Sealy Townsend and Robert A. Millikan further investigated electrons and were able to determine their exact charge and mass. -
1900
Antoine Becquerel discovered that electrons and beta particles were the same thing. -
1903
Ernest Rutherford decided that radioactivity is what caused atoms to be broken down. -
1911
Ernest Rutherford and Hans Geiger discovered that electrons moved around the nucleus of the cell's atom much like planets orbit the sun. -
1913
Niels Bohr discovered the electrons' orbits and that there were more electrons in the outer orbits than in the inner orbits. He also saw that radiation was emitted when an electron would jump from one orbit to another. -
1914
Ernest Rutherford discovered protons in the nucleus. -
1914
Henry Moseley labeled the elements with atomic numbers based upon the number of electrons in an atom rather than on their atomic mass. -
1932
James Chadwick discovered neutrons and identified isotopes. -
1932
J. D. Cockroft and Ernest T. S. Walton worked together in splitting the atom when working with lithium which they bombarded with protons. The lithium nucleus was divided into two helium nuclei. -
1932
Ernest O. Lawrence, Milton Stanley Livingston and Milton White worked on the first cyclotron at the University of California in Berkeley.
