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Chapter 4 (The Atom Scientist (J. J. Thomson (J.J Thomson discovered that…
Chapter 4
The Atom Scientist
J. J. Thomson
J.J Thomson discovered that by passing electric current through gases at low pressure then discovering that the electron can become + and - charged. Thomson had discovered the Cathode Ray.
Robert Millikan
Robert Millikan carried out experiments to find the quantity of charge carried by an electron. Millikan used the value and the charge-to-mass ratio of an electron measured by Thomson, he calculated the mass of the electron.
John Dalton
By using experimental methods, Dalton transformed Democritus’s ideas on atoms into a scientific theory. Dalton formulated a hypothesis and theories to explain his observations. This experiment resulted in Dalton’s atomic theory.
Ernest Rutherford
Ernest Rutherford discovered in the nuclear atom, the protons and neutrons are located in the nucleus. The electrons are distributed around the nucleus and occupy almost all the volume of the atom. Experiments used were Rutherford’s Gold-Foil Experiment & The Rutherford Atomic Model.
Democritus
Democritus discovered that atoms were indivisible and indestructible. Although Democritus’s ideas agreed with later scientific theory, they didn’t explain chemical behavior. Also lacked experimental support, because it was not based on scientific method.
James Chadwick
By measuring velocities, he was able to show that the new particle has essentially the same mass as a proton. A small summary of an experiment that James Chadwick did was he was measuring velocities
Parts of the Atom
Atomic particles. Protons and neutrons are heavier than electrons and reside in the nucleus at the center of the atom.
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Ions v. Isotopes
An ion is an atom with a net electric charge due to the loss or gain of one or more electrons. An isotope is each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties.