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John Dalton
proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together. -
Dmitri Mendeleev
Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". and that is now known as the "Periodic table" -
James clerk maxewell
put forward the theory of electromagnetism and made the connection between light and electromagnetic waves -
Sir William Crookes
Discovered cathode rays had these properties:
1. travel in straight lines from the cathode
2. causes glass to fluoresce
3. impart a negative charge to objects they strike
4. are deflected by electric fields and magnets to suggest a negative charge -
Frederick Soddy
Came up with the term "isotope" to explain the unintentional breakdown of radioactive elements. -
Rutherford
described the atom as a tiny, dense, positively charged core called a nucleus -
Hans Geiger
German physicist who introduced the first successful detector (the Geiger counter) of individual alpha particles and other ionizing radiations -
Niels Bohr
proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit. -
Schrodinger
Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom -
Modern day theory
Present-day atomic theory is largely based on concepts proposed in the 1920's by the Austrian Erwin Schrdinger, the Germans Werner Heisenberg and Max Born, Paul Dirac of Great Britain, and Louis de Broglie of France
