HISTORY OF THE ATOM

Democritus

DEMOCRITUS

• He lived 460 bc - 370 bc and lived in Abdera
• Democritus adopted the atomic theory
• This states that "The universe is composed of two elements: the atoms and the void in which they exist and move."
• This is exactly his theory. 1.All matter consists of invisible particles called atoms. 2. Atoms are indestructible. 3. Atoms are solid but invisible. 4. Atoms are homogenous. 5. Atoms differ in size, shape, mass, position, and arrangement. ->Solids are made of small, pointy atoms. ->Liquids are made of large, round atoms. ->Oils are made of very fine, small atoms that can easily slip past each other. Basically he made a hypothesis and tested this thus creating the atomic model and helped further the atoms understanding. He tested this in 400 bc
• He was an intelligent man, who enjoyed traveling , published over 70 books yet never got married.

J.J THOMSON

• He was born December 18th 1856 and died August 30th 1940. Was born in cheetham hill
• He discovered a method that separates different kinds of atoms and molecules from the use of positive Rays. He also discovered electrons and noticed the atom can be divided.
• He found this by contributing with other scientifically intelligent men such as Aston & Demper. Including this he also created the Plum Pudding Model. This shows that electrons are surrounded by a "pudding" of positive charges to balance the negative.
• J.J attended the Owens college in Manchester and then to the Trinity college. He won the Adams prize in 1884 in credit to his book "treatise on the motion of vortex rings"

J.J THOMSON

ERNEST RUTHERFORD

• Born on August 30th 1871 and died October 19th 1937. Was born in New Zealand
• Frederick Soddy arrived at McGill in Montreal in 1900 from Oxford, and he collaborated with Rutherford in creating the "disintegration theory" of radioactivity which regards radioactive phenomena as atomic - not molecular. In 1910, his investigations into the scattering of alpha rays and the nature of the inner structure of the atom which caused such scattering led to the postulation of his concept of the "nucleus", his greatest contribution to physics. In 1919, he discovered that the nuclei of certain light elements, such as nitrogen, could be "disintegrated" by the impact of energetic alpha particles coming from some radioactive source, and that during this process fast protons were emitted.
• J.j disproved the plum pudding model and furthered our understanding of the nucleus.
• In addition to his success he was awarded two medals the Rumford medal and the Copley medal. Rumford was also an author and they were mostly about the topic of atoms.

THE ALPHA RAYS BY ERNEST RUTHERFORD

JAMES CHADWICH

• Cheshire,England. He was born on October 20th,1891. He died on July 24,1974.
• Chadwick made a fundamental discovery in the doorman of nuclear science. He proved the existence of neutrons.
• He established that atomic number is determined by the numbers of protons in an atom. He also discovered the fourth subatomic particle,the neutron. (1932)
• During the time he was alive World War II was taking place. Died in Cambridge,Endinburg

JAMES CHADWICH

Antoine Lavoisier

• He lived in France from 1743-1794
• He began the conversation on what an atom was exactly
• One of his experiments was turning HgO into Hg+O. He used this experiment to help himself come up with the Law of Conservation. The law states that matter cannot be made or destroyed. He also hints at the rearrangement of matter in reactions.
• Did you know he was suspense tend of treason during the French Revolution.
• Was a lawyer, an accountant and a scientist.

ANTOINES LAW EXPLAINS

ROBERT MILLIKAN

• Born in Morrison Illinois1868–1953 moved to Ohio at age 7.
• He created an oil drop experiment which erasures an electrons charge.Millikan's oil-drop experiment involved spraying oil from a perfume atomizer into a sample chamber. Some of the droplets traveled through a pinhole into a space between two plates, one of which had a negative electric charge and the other of which had a positive charge. This central chamber was then ionized with X-rays. Particles that failed to catch electrons followed gravity to the bottom plate, while particles that managed to catch at least one electron floated up to the positive plate or fell at a slower rate of speed. Millikan reached the conclusion that each drop had a charge that was a multiple of 1.59 x 10^(-19) Coulombs.
• He won the noble prize in 1923 in physics.
• In his sophomore year in college at Oberlin he was asked to teach an introductory-level physics class

ROBERT MILLIKAN

NIELS BOHR

• Born: 7 October 1885, Copenhagen, Denmark Died: 18 November 1962, Copenhagen, Denmark
• 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. Bohr's theory could explain why atoms emitted light in fixed wavelengths.
• 1913-1914 Bohr held a Lectureship in Physics at Copenhagen University and in 1914-1916 a similar appointment at the Victoria University in Manchester. In 1916 he was appointed Professor of Theoretical Physics at Copenhagen University

NIELS BOHR

JOHN DALTON

• September 6, 1766, in Eaglesfield, England- 1844
• Daltons theory
• 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms.
• Now we know that atoms can be destroyed by nuclear reactions vs. chemical reactions.
• Did you know dalton was color blind? Dalton was also a pioneer, meteorologistwho kept the weather for 57 years.

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CITATIONS

• https://the-history-of-the-atom.wikispaces.com/Democritus
• https://the-history-of-the-atom.wikispaces.com/J.J.+Thomson
• https://the-history-of-the-atom.wikispaces.com/Ernst+Rutherford
• http://jameschadwickatomictheory.weebly.com
• http://historyoftheatomictheory.weebly.com/antoine-lavoisier.html
• http://www.chemistryexplained.com/Ma-Na/Millikan-Robert.html
• http://www.iun.edu/~cpanhd/C101webnotes/composition/dalton.html