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John Dalton
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Inspiration of Dalton’s Gas Experiments
What Inspired Him: The attempts to find out what precisely inspired Dalton to come up with this theory is unknown. -
Dalton’s Gas Experiments
Experiment Description: Dalton performed several experiments on gases. He would carefully measure the volume of the gases and noticed that gasses always combined in whole number ratios. -
Dalton’s Impact
What Was Learned: That everything is made up of small spheres. -
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Joseph John Thomson
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Robert Andrews Millikan
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Ernest Rutherford
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Niels Bohr
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Thomson’s Cathode Ray Tube Experiment Inspiration
What Inspired Him: Thomson became interested in the equations developed by James Clerk Maxwell that showed that electricity and magnetism belonged to a single force, the electromagnetic field. This force is an important piece in his cathode ray tube experiment. -
Thomson’s Cathode Ray Tube Experiment
Experiment Description: In Thomson’s cathode ray tube experiment, a beam of cathode rays shoots through a cathode ray tube. Two oppositely charged plates surround the rays. The beam was deflected away from the negative plate and diverged towards the positive plate. -
Thomson’s Influence
What Was Learned: The beam changing its path towards the positive plate indicated that there must be a source of negative charge inside of the atom. Because Thomson knew that all atoms were neutral, he reasoned that there must be some sort of positive charge within the atom to balance out the negative charge. Thomson discovered the electron. He proposed a model of the atom that consisted of a sea of positively charged matter with negatively charged particles roaming within it. -
Thomson’s Model
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Millikan’s Oil Tube Experiment’s Inspiration
What Inspired Him: J.J. Thomson’s cathode ray tube experiment allowed him to find the charge to mass ratio of the electron, but no one was able to calculate the charge or mass independently. This provoked Millikan to conduct the oil drop experiment. -
Millikan’s Oil Drop Experiment (Part 1)
Experiment Description: Oil droplets (negatively charged) are sprayed into a chamber. The droplets fall between two plates that Millikan could control the voltage/charge of, the top being positive and the bottom being negative. Some larger droplets would fall to the bottom because the force of gravity overpowered the electric attraction to the positive top plate. Other smaller droplets would stick to the top plate because the electric force overpowered the force of gravity. -
Millikan’s Oil Drop Experiment (Part 2)
Experiment Description continued: However, a few would be suspended in between the two plates. This is because the two forces were balanced. Millikan then calculated the volume by finding the diameter of the droplet. Next, he used the density formula to find the mass of the droplet. Finally, he found that when mass was divided by charge, the quotient was always some multiple of a fundamental unit of charge (9.31E-19). -
Rutherford’s Gold Foil Experiment Inspiration
What Inspired Him: Rutherford wanted to test Thomson's theory that an atom's mass and charge are uniformly distributed throughout the atom. -
Rutherford’s Gold Foil Experiment
Experiment Description: To test Thomson's theory they shot alpha particles through a thin piece of gold foil. They expected close to no alpha particles returning or changing directions. During the experiment some of the alpha particles started to return and turn weird angles. 1 out of 8000 alpha particles would return. -
Rutherford’s Impact
What Was Learned: The alpha particles returning showed that there is a nucleus in atoms. Also because the nucleus is so small most of the atoms are empty. That is why some of the particles would return because the nucleus would bounce off the gold foil particles. -
Bohr’s Thought Experiment’s Inspiration
What Inspired Him: Rutherford's model of the atom would lead to the electrons surrounding the nucleus to be sucked towards the nucleus and cause the atom to collapse. This led Bohr to come up with a better model, in 1913. -
Bohr’s Thought Experiment and Influence
Experiment Description: He proposed the idea that electrons can only exist in certain energy levels. He proposed that the electrons orbit the nucleus in these circular rings. The electrons would orbit in different rings according to the atom's energy level. The higher the energy level, the larger and further up away from the nucleus the electrons orbit. -
Bohr’s Model
