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John Dalton
Proposed an ¨atomic theory¨ with spherical solid atoms based upon measurable properties of mass. -
Dalton's Model
He came up with this Atomic theory as a final result of his investigation into gases. He discovered that certain gases can only be combined in certain proportions, even if two different compounds shared same element or group elements. -
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. -
J.J. Thomson
Used a CRT(Cathode Ray Tube) to experimentally determine the charge to mass ratio of an electron. -
J.J Thomson's Model
Thomson's model of atomic structure is often called the plum pudding model. He postulated that the negatively charged electrons, he had recently discovered, were scattered throughout a cloud of positive charge, like the plums in plum pudding. -
Ernest Rutherford
Using alpha particles as atomic bullets, probed the atoms in a piece of thin gold foil . Established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus.
Gold Foil Experiment: This experiment was determined to find out the structure of an atom. -
Rutherford Model
This model can also be called nuclear atom, or planetary model of the atom. What this model describes is that it describes the atom as a positive charged core called nucleus, tiny ,dense, in which all mass is concentrated. -
James Chadwick
Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. -
Niels Bohr
Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons. -
Borh Model
The atom consists of a nucleus with electrons orbiting at specific energy levels. Absorbed photons cause electrons to jump between energy levels. -
Quantun Mechanical Model
Electrons are defined as standing waves. The electron probability distribution gives the areas in which the probability of electron presence is high.
