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John Dalton's Experiment
Dalton's atomic theory contains five basic assumptions:
- All matter consists of tiny particles called atoms
- Atoms are indestructible and unchangeable
- Elements are characterized by the weight of their atoms
- In chemical reactions, atoms combine in small, whole-number ratios
- When elements react, their atoms may combine in more than one whole-number -
J.J. Thompson’s experiment
Thomson realized that the accepted model of an atom did not account for negatively or positively charged particles. He discovered that electrons were negatively charged, but not protons as positively charged. -
Albert Einstein's Experiment
Einstein theorized the presence of electrons that are produced when a beam of light is directed onto the surface of metal -- this is known as the photoelectric effect. The release of atoms caused by the photoelectric effect was theorized to form an electrical current. This theory challenged the idea that light traveled only in waves. -
Robert Milikan's Experiment
Robert Millikan determined the unit charge of the electron with his oil drop experiment. He calculated the mass of electron and positively charged atoms. -
Millikan's oil drop experiment
Millikan’s and Fletcher's apparatus incorporated a parallel pair of horizontal metal plates. By applying a potential difference across the plates, a uniform electric field was created in the space between them. A ring of insulating material was used to hold the plates apart. Four holes were cut into the ring, three for illumination by a bright light, and another to allow viewing through a microscope. -
Ernest Rutherford's Experiment
Rutherford aimed alpha particles at solid substances such as gold foil and recorded the location of the alpha particle "strikes" on a fluorescent screen as they passed through the foil. To the experimenters’ amazement, although most of the alpha particles passed unaffected through the gold foil as expected, a small number of particles were deflected at an angle, and a few ricocheted straight back. Rutherford concluded that the atom consisted of a small, dense, positively charged nucleus & electr -
Neils Bohr’s experiment
Description: Bohr proposed that electrons are arranged in concentric circular orbits around the nucleus. This model is patterned on the solar system and is known as the planetary model. The four main principles are:
- Electrons occupy only certain orbits around the nucleus. Those orbits are stable and are called "stationary" orbits.
- Each orbit has an energy associated with it. The orbit nearest the nucleus has an energy of E1, the next orbit E2, etc.
- Energy is absorbed when an electron jump -
Erwin Schrödinger’s experiment
Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.
