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450 BCE
Greek philosopher Democritus
Democritus' model of the atom was a sphere. He simply theorized that everything was made up of small indivisible particles of matter, which he called atoms. -
John Dalton
John Dalton's model for the structure of the atom was the same as Democritus', that the atom was the smallest unit of matter. In addition to other changes in atomic theory, John Dalton suggested that there were different types of elements, and attempted to calculate their relative weights. -
John Dalton
John Dalton's "experiments" consisted of observing chemical reactions. By observing different reactions and performing calculations he was able to determine what he thought were the relative weights of different atoms. -
J.J Thomson
John Dalton's "experiments" consisted of observing chemical reactions. By observing different reactions and performing calculations he was able to determine what he thought were the relative weights of different atoms. -
J.J Thomson
J.J. Thomson's Cathode Ray Tube Experiment helped him discover electrons. In the experiment, an electric field was created around the cathode ray tube, and after certain particles moved to the positive part of the field, J.J. Thomson was able to conclude that there were smaller negatively charged particles in the atom. He was also able to determine the charge to mass ratios of the electrons from this, and it helped him devise the "plum pudding" model of the atom -
Ernest Rutherford
Ernest Rutherford's model of the atom contains a nucleus and electrons, and is known as the "planetary" model of the atom, because of the orbit of the electrons. The positively charged nucleus lies in the center of the atom, and the negatively charged electrons orbit around it. -
Ernest Rutherford
Gold Foil Experiment consisted of firing alpha particles at a thin sheet of gold foil, and observing where they ended up using a zinc sulfate sheet to record their location using light. The results of the experiment were that most of the alpha particles went straight through the gold foil. This instead led him to think that there is a small area of positive charge in the center of the atom, and led him to create a new model of the atom. -
Niels Bohr
Niels Bohr's model of the atom consisted of having electrons orbit the nucleus at certain energy levels or in certain electron shells. His model also included the idea that electrons can jump between levels by either absorbing or emitting energy. -
Erwin Schrodinger
Erwin Schrödinger's Quantum Mechanical model of the atom consisted of having electrons orbit around the nucleus in non-circular orbits. Instead of showing where specific electrons were on their paths orbiting the nucleus, Erwin Schrödinger depicted the probability of where an electron could be. The darker areas in the model are more likely to contain an electron than the lighter areas.
