History Of The Atom

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History Of The Atom


370 BC.





History Of The Atom


Democritus really didn't have any equipment so he never got the chance to experience with atoms. He just visualized that matter was made of small things. Democritus called these atoms. The issues with his claim was that he had no nucleus, no sub-atomic particle and no electron cloud and that they were invisible.


Dalton saw atoms as solid spheres that were tiny and indestructable. He also said that atoms combine to make whole ratio compunds and that all atoms were the same. Dalton also said that atoms cannot be destroyed during chemical reaction. Unfortunately, Dalton never did any experimenting. The problem with Daltons theory is that he never mentioned a nucleus, he said they were all the same shape, no subatomic particles, and no isotopes.

Thomson discovered that atoms have electron and at the moment he called them corpucles. Thomson imagined them to be almost like cookie dough he thought that the electrons were spread out on one big positive circle. Thomson discovered the electron by a cathode ray tube with metal cylinders on each end. The cylinders were connected to a electometer a device that measured the electrical charge. Thomson used a vaccum tube with metal plates at both ends and an electrical source for his experiment. He found that a beam would form between two plates the cathode and the anode he then put a magnet near the beam. The magnet caused it to bend which meant the beam was electrically charged. Thomson discovered that the rays were negatively charged particles which were electrons. Whats wrong with Thomson was that he didn't have electron around nucleus, no set nucleus, one big circle. Thomson had no electron energy levels and no neutrons.

Neils Bohr discovered that electrons are in energy levels around nucleus. Neils Bohr saw that electrons are impossible to fall in to the nucleus. Neils Bohr discovered this through an experiment with light and hydrogen. He shot the light at the prism which split. Bohr saw a line of light where he would see an electron. Neil Bohr concluded that the electons must be in specific orbitals. The problem with Neil was that he only experimented with Hydrogen which only had one electorn.

Ernest Rutherford thought that the atom had a positive nucleus and electrons were floating around. Rutherford also thought that all the mass was in the nucleus and the rest was empty space. Ernest discovered this nucleus through his Gold Foil experiment! In the experiment he beamed charged particles to a thin thin sheet of gold foil. When only some particles passed, and some deflected Rutherford said that the gold must hasve some positive charge. The mass of the that positive charge was what he called the nucleus. The problem with this is that he had no neutrons inside the nucleus, and no electron levels.

James Chadwick proved the existance of neutrons and that the atomic number is based of the number of protons. James Chadwick proved this through shooting alpha particle toward berryllium and from there neutral waves were given off to fall on the parrafin wax. From there the parrafin wax would give off protons to the detector and counter of the protons. From this Chadwick concluded that there was a neutron that had almost the same amount of mass as a proton.

Robert Millikan found the charge of an electron. Robert Millikan found it through allowing a spray of oil to settle through a whole into a chamber where he could observe their fall. The top and bottom of the chamber were electrically charge plates where he introduced x-rays. The charges produced by the x-rays attached to the oil droplets. Millikan then applied a voltage and the ones that would fall slowly were the electrons by turning the voltage on and off and lowering and making it higher he figured out the charge of an electron which were all multiples of 1.6x10^-19. The problem with Rob was that he still had no neutrons.

Erwin Schrodinger discovered that the electron is in a ceratin position. Erwin saw that when the cloud is most dense it is most likely to find the location of the electron. Erwin thought that electrons were both particles and waves. Erwin made an anology to a cat also being alive and dead at the same time just like electrons beng particles and waves at the same time. Erwin didn't really experiment he worked with math equation. The problem with Erwin visualization was that he had no neutrons.


John Dalton

Robert Millikan

JJ Thomson

Ernest Rutherford

Neils Bohr

Erwin Schrodinger

James Chadwick

Noemi Torres


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