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400
Leucippus- ( 480-420 B. C. E)
Leucippus is best known for being the first to come up with the theory of the atom (atomos- meaning uncuttable) during the fifth century B.C. He believed that the universe consisted of two different elements which were the solid and the void. Both of which are infinite and make up everything. With such a discovery the atomic theory began. Propsing that the building blocks of everything was composed of atoms. -
400
Democritus- ( 458- 370 B. C.E)
Democritus was a student of Leucippus and strongly believed and contributted to the atomic theory. Along with his teacher he did not accept Eleatic hypothesis that "everything is one" and that change and motion is an illusion. He believed that atoms existed in diffrent shapes and motions which created everything that one sees in the universe. Unlike the common belief that everything was made out of fire, Earth, wind, and water. -
400
Greek atomic model (Major Event)
Propesed by both Democritus and Leucippus. -
Period: 400 to
Atomic TImeline
During the year 400 B.C to the year 1972 Scientist and philosphers have been trying to understand the concept of what makes everything. When the atom was discovered scientist focused on the issue, What makes up an atom? And What does it look Like? -
450
Aristotle- (384- 322 B.C.E) Most research done during the 300s. B.C
Aristotle, like many other philosophers, attacked Democritus and Leucippus theory of atoms. He believed more on the fact that everything was composed out of fire, water, earth, and air like his predecessors. That these four elements combined to form everything and that two forces acted upon it. One was Levity which made fire and air rise. And the other was gravity which made Earth and water sink. It would take another 2000 years for Democritus theory to be revived. -
John Dalton- (1766-1844) Discovery done during the year 1803
Considered the father of modern atomic theory Dalton was the first in 2000 years to come up with the atomic theory. Due to his interest in meteorology he took up to studying gasses and while experimenting with gases he found out that they react with one another and in this way he discovered Hydrogen in the periodic table and with the help of ancient text he figured out the name of his ideas, The Atom. -
John Dalton part II during the year 1803
He believed that these Atoms were round particles which made up all matter and that each element differed with each other only by their weight. -
John Dalton years 1808-1827 (Major Event)
Dalton's theory was presented in the New systems of Chemical property which stated that all matter was composed of small indivisible particles termed atoms, atoms of a given element possesd unique characteristics and weight, and three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules). -
William Thomson- ( 1824- 1907)
Both Mathematician and physicist William Thomson was the first to try and construct a physical model of the atom. Inspired by Helmholtz who proposed that an vortex line has the same particles and thus is unbroken making it ring like. It was this that made Thomson believe that atoms were like vortices . -
J.J thomson Part II
Due to his study of the positively charged particles he led to the development to the mass spectrograph. Which in turn enabled him to discover isotopes. (atoms of the same atomic number, but different weight.) Thomson work has benefited the atom community of scientist by also explaining chemical bonding and its molecular structure. -
Joseph John Thomson- ( 1856- 1940)
J.J Thomson was the first to find that an atom had an electron in the year 1897. The experiment that yielded such a discovery was made to study the electric discharge in a vacuum. During the experiment he interrupted the rays electrically charged plates and magnets. This concluded that there is something much smaller than atoms which gave a significant difference to the charge to mass ratio. -
Electron (Major Event)
J.J Thomson discovery of the electron came out of curiosity when he was conducting an experiment which involved a ray of electricity being passed through a vacuum tube. A mysterious light would appear because of this and it was Thomson who discovered that it would bend slightly towards a positively charged plate. Thus the negatively charged electron was discovered.charged plate. Thus the negativley charged electron was discovered. -
Plum Pudding model (Major Event)
proposed by J.J Thompson it was the first to show electrons, but it excluded the nucleus. -
Robert Andrews Millikan- (1868- 1953)
Robert Millikan was able to identify the charge of an electron using his oil drop experiment during the year 1910. Which gave way to the calculation of the mass of an electron and the positively charged atom. -
Ernest Rutherford- (1871- 1937)
Ernest Rutherford was a student under J.J Thomson. Making it only a natural that he chose to follow in his foot steps. He, however, started a new atomic model which showed that the positively charged is inside a tiny nucleus which is ten thousands times smaller than the entire atom. With the electrons being father apart from the nucleus. Meaning that everything in universe is made up of empty space. -
Rutherford atomic model (Major Event)
made my Rutherford. Not only did it include the nucleus and showed that electrons orbit the nucleus. -
Ernest Rutherford part II
And since the nucleus is so small and the electron is father apart from it he stated that most of the universe was composed of empty space. Along with discovering that he also discovered the positively charged neutron -
Gold foil experiment (Major Event
The famous gold foil experiment was done by Rutherford. This experiment involved the firing of radioactive particles through a gold thin metal foils and detecting them using screens coated with zinc sulfide. Rutherford found that although most of particles passed straight through the foil about 1 in 8000 were deflected leading him to his theory that most of the atom was made up of 'empty space'. -
Niels Bohr- (1885- 1962)
Niels Bohr contribution to the atom model helped greatly improve our understanding of the atom in general. He was only able to do so thanks to Rutherford early model of the atom saying that it had a positively charged nucleus with a negatively charged electron orbiting the nucleus. Bohr then proposed that electrons orbited in larger orbits and that the farther away the electron is from the nucleus the more electrons that layer can hold. And it is this that determines the chemical property. -
Bohr's model (major event)
Bohr propesed that the electrons orbited the nucleus much the way that planets do to the sun. He aslo stated that the nucleus of an atom is much tinier than once thought and that the electrons themselves are father apart from the nucleus. Along with showing that their were diffrent electron clouds in which the electrons were found. -
Niels Bohr Part II
He later on also suggested that atoms emitted radiation when they jump from outer orbit clouds to the inner ones. -
Erwin Schrodinger- (1887-1961)
Erwin Schrodinger came and finalized the puzzle about the electron arrangement. He stated that electrons behave more like waves and for this reason could not be precisely calculated. He also theorized that each electron had a sub shell equal to the number shell number. -
Werner Heisenberg- (1901-1976)
Werner Heisenberg is one of the chief reasons to the breakthrough of quantum mechanics. With his quantum- theoretical reformulation which explains the energy conservation in the atomic process. -
Quantum Mechanical atomic model (Major Event)
developed by Erwin Schrodinger the quantum mechanical model states that the posistion and momentum of an electron cannot be determined at the same time. and that the number of energy levels for electrons is a result due to their wave like properties. -
Paul Dirac- (1902-1984)
Dirac is most renowned for his theory of antimatter. Inspired by Albert Einstein, Niels Bohr, and Werner Heisenberg he was able to apply quantum mechanics with James Maxwell’s theory of electromagnetism to establish the quantum field theory. He also used his version of quantum mechanics to develop his transformation theory. -
Paul Dirac Theory of antimatter (Major event)
pointed out that every single particle has an anti-particle that through contact form burst of energy. He was able to discover this while formulating an equation for electrons. -
James Chadwick- (1891-1974)
Even though Rutherfod was the first to propose that a neutrally charged particle existed in the atom it was Chadwick who was able to discover it. Using a complex experiment to determine what it was. Taking a sample of Beryllium he bombarded it with alpha particles which emitted a mysterious radiation. After a few more test all that was left for Chadwick to do is to make it all fit together. -
James Chadwick Part II
He knew it was neutral because it wasn’t affected by the magnetic field and he also knew that it wasn’t radiation. He finalized that this new particle had to be the neutral particle he was looking for and named it the Neutron.
