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Period: 405 to 454
Democritus Life Span
Democritus 460 – 370 BCE) was an Ancient Greek philosopher born in Abdera, Thrace, Greece. -
432
Democritus Atomic Theory
Democritus claimed that everything is made up of atoms. These atoms are physically, but not geometrically, indivisible; between atoms lies empty space; atoms are indestructible; have always been, and always will be, in motion; there are an infinite number of atoms and kinds of atoms, which differ in shape, and size. He said, about the mass of atoms,”The more any indivisible exceeds, the heavier it is.”. He helped to propose the earliest views on the shapes and connectivity of atoms. -
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John Dalton's Life Span
Chemist John Dalton was born September 6, 1766, in Eaglesfield, England. During his early career, he identified the hereditary nature of red-green color blindness. In 1803 he revealed the concept of Dalton’s Law of Partial Pressures. Also in the 1800s, he was the first scientist to explain the behavior of atoms in terms of the measurement of weight. Dalton died July 26, 1844 in Manchester, England. -
Dalton's Atomic Theory
John Dalton originated the modern atomic theory in the eraly 19th century. He proposed the Atomic Theory in 1803 which stated that, all matter was composed of small indivisible particles termed atoms; atoms of a given element possess unique characteristics and weight, and three types of atoms exist: simple, compound, and complex. -
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JJ Thompson's Life Span
-Sir Joseph John "J. J." Thomson (18 December 1856 – 30 August 1940) was a British physicist. In 1897, Thomson showed that cathode rays were composed of a previously unknown negatively charged particle, and thus is credited with the discovery and identification of the electron. Thomson is also credited with finding the first evidence for isotopes of a stable (non-radioactive) element in 1913 as part of his exploration into the composition of canal rays (positive ions) and with the invention of t -
Marie Curie's Atomic Theory
Marie and Pierre Curie enhanced the understanding of radioactivity through their research of radioactive materials (discovering radium and polonium). This helped to show what happened when atoms were affected and observed.Date Adopted: 1898The Curies shared a Nobel Prize with Henri Becquerel. -
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Ernest Rutherford's Life Span
Ernest Rutherford was born on August 30, 1871. He died on October 19, 1937. Country of Origin-New Zealand. Responsible for a remarkable series of discoveries in the fields of radioactivity and nuclear physics. He discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei. Most important, he postulated the nuclear structure of the atom: experiments done in Rutherford's laboratory showed that when alpha particles are fired into gas. -
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Neils Bohr's Life Span
Neils Bohr was born on October 7, 1885. He died on November 18, 1962.
Country of Origin-Denmark -
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James Chadwick's Life Span
James Chadwick was born on October 20, 1891 and died on July 24 1974. Country of Origin-England.Chadwick made a fundamental discovery in the doorman of nuclear science. He proved the existence of neutrons. James predicted the atom would have a neutron. He established that atomic number is determined by the numbers of protons in an atom. He also discovered the fourth subatomic particle,the neutron. James was most famous for his discovery of the neutron in an atom. -
J.J, Thompson's atomic theory
J.J. Thomson or Sir Joseph John Thomas won the Nobel Prize for his discovery of an Electron in 1897. Sir J.J. Thomson was from the United Kingdom and attended Cambridge University in Cambridge, Great Britain. J.J. Thomas also discovered the Plum Pudding Model. This shows that the atom contains electrons surrounded by a cluster of positive charges to balance the electron’s negative charge. -
Ernest Rutherford's Atomic Theory
Ernest Rutherford attended Cambridge University and worked with Professor J.J. Thomson. Mr. Rutherford invented a detector for electromagnetic waves. He also established the existence of the alpha and beta rays in uranium radiation and indicated some of their properties. Rutherford was inspired to ask Geiger and Marsden in this experiment to look for alpha particles with very high deflection angles, of a type not expected from any theory of matter at that time. Er -
Niels Bohr's Atomic Theory
Niels Bohr attended Copenhagen University where he also studied under J.J. Thomson. He developed a model of a hydrogen atom and also a theory that states that electrons travel in certain orbits around the atom’s nucleus. The chemical properties of an element being determined mainly by the number of electrons present. The picture above is of the planetary model which was founded by Bohr and Rutherford in 1913 that shows a positive charged nucleus surrounded by electrons that orbit the nucleus. -
Electron Cloud
The Electron Cloud model was really invented between three different scientists, Ernest Rutherford, Niels Bohr, and Werner Heisenberg.The electron cloud model is an atom model wherein electrons are no longer depicted as particles moving around the nucleus in a fixed orbit. Instead, as a quantum mechanically-influenced model, we shouldn’t know exactly where they are, and hence describe their probable location around the nucleus only as an arbitrary ‘cloud’. -
Erwin Scrodinger
Erwin Schrodinger was born on August 12,1887 and died on January 4, 1961. Erwin Schrodinger is famous for a paper he wrote called Quantisierung als Eigenwertproblem which was based on wave mechanics and is known today as the Schrodinger equation. This paper has been noted that it is the most important advances of the twentieth century and created major advances in both chemistry and physics. -
James Chadwick's Atomic Theory
James Chadwick discovered the particle in the nucleus of an atom that became known as the neutron because it has no electric charg e. For this discovery he won the Nobel Peace Prize. Before his discovery he was in a German internment camp during World War I and there he was allowed to start his laboratory work. -
Aristotle's Atomic Theory
Aristotle said that atoms were composed of the four elements: fire, water, earth, and air. Each of these atoms had certain properties depending on what they were made of: hotness, dryness, wetness, or coldness. This contradicted the work of Democritus and put a second theory in use for almost 2000 years (before it was disproved). He also originated a method of gathering scientific facts and recording them methodically.Aristotle admired Democritus as a role model.
