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Dalton's Theory
John Dalton pictures atoms as tiny, indestructible particles, with no internal structure. -
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". This became known as the Periodic Law. http://atomictimeline.net/ -
Sir William Crookes
Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. http://atomictimeline.net/ -
Thomson Theory
J.J. Thomson, a British scientist, discovers the electron. The later leads to his "plumpudding" model. He pictures electrons embedded in a spere of a positive electrical charge. -
Albert Einstein
Made the formula E = mc2 -
Rutherford's Theory
New Zealand physicist Ernest Rutherford finds that an atom has a small, dense positively charged nucleus. Electrons move around the nucleus. -
Bohr's Theory
In Niels Bohr's model, the electron moves in a circular orbit at fixed distances from the nucleus. -
Wolfgang Pauli
Austrian physicist, Wolfgang Pauli predicted that an electron should spin (kind of like a top) while it orbits around the nucleus. The electron can spin in either of two direction. This spin consisted of a fourth quantum number: electron spin. -
Elctron Cloud
Erwin Schrodinger develops mathmatical equations to describe the motion of electrons in atoms. His work leads to the electron cloud model.
