c.460 BC- Democritus
Lived in Abdera, Greece in c.460 BC
He proposed that atoms and the void are the only things that actually exist. He elaborated on how nature behaves and how atoms move randomly and collide to form larger bodies. Democritus believed that this idea of atoms colliding is what made larger bodies, and that this is how the world began.
Democritus was inspired by his teacher, Leucippus. Leucippus began discovering things about the atom. Democritus took the basis of his mentors findings, and furthered his research.
An interesting fact about Democritus is that he is considered "The father of modern science".
"How Did Democritus Contribute to the Atomic Theory?" Reference. N.p., n.d. Web. 18 Jan. 2017. <https://www.reference.com/science/did-democritus-contribute-atomic-theory-4653045c78e24bd4>.
1743- Antoine Lavoisier
Lived in Paris, France in 1743
Antoine found that mass is conserved in a chemical reaction. His favorite experiment was turning HgO into Hg+O. This experiment led him to the discovery of the Law of Conservation. This law states that matter can't e created or destroyed. He also began the conversation on what an atom was exactly.
The way that he came about discovering the Law of Conservation was by experimenting. His favorite experiment, which was turning HgO into Hg+O, is what led him to the discovery.
An interesting fact about Antoine is that he was suspected of treason during the French Revolution.
"Antoine Lavoisier." History of the Atomic Theory. N.p., n.d. Web. 18 Jan. 2017. <http://historyoftheatomictheory.weebly.com/antoine-lavoisier.html>.
1803- John Dalton
Lived in Manchester, England in 1803
John Dalton came up with his own concept of Dalton's Theory:
- matter is composed of extremely small particles called atoms
- atoms are indivisible and indestructable
- atoms of a given element are identical in size, mass, and chemical properties
- atoms of specific elements are different than those of other elements
- in a chemical reaction, atoms separate, combine and/or rearrange
Dalton did tons upon tons of library research to come up with his theory. He looked at almost every scientist or philosopher in history who had any conception of atoms whatsoever.
An interesting fact about John Dalton is that he was a Quaker.
"John Dalton." History of the Atomic Theory. N.p., n.d. Web. 18 Jan. 2017. <http://historyoftheatomictheory.weebly.com/john-dalton.html>.
1858- Max Planck
Lived in Kiel, Germany in 1858
In 1899, he discovered a new fundamental constant, which is named Planck's constant, and is, for example, used to calculate the energy of a photon. Also that year, he described his own set of units of measurement based on fundamental physical constants. One year later, he discovered the law of heat radiation, which is named Planck's law of black body radiation. This law became the basis of quantum theory, which emerged ten years later in cooperation with Albert Einstein and Niels Bohr.
Max Planck Atomic Theory:
- Atomic theory owes a lot to the Planck Quantum theory. The revolution of electrons round the nucleus and the energy of the orbits being discrete is based on the Planck's quantum theory.
- The electron with its negligible mass behaves like a photon in its revolution and is called photo electron. This theory is put forward by Albert Einstein in his Photo electric effect.
- Thus every electron in an atom has its own discrete energy and moves around the nucleus. If external energy is supplied to an electron it gets excited and goes to a higher orbit.
- When it returns to its normal state, it releases the absorbed energy. This is the basis of the hydrogen spectrum and thus the establishment of radius, velocity and energy of an electron and orbit.
The experiment Max Planck performed to establish his theory of energy radiation in packets called quanta consisted of a set of oscillators and spectroscope to measure the wavelength. Max Planck performed such experiments with wide range of spectral frequencies and established his quantum theory.
An interesting fact about Max Planck is that he was given the Nobel Prize in Physics in 1918.
"Max Planck, Inventor of Quantum Theory." Max Planck, Inventor of Quantum Theory - Timeline Index. N.p., n.d. Web. 18 Jan. 2017. <http://timelineindex.com/content/view/1203>.
1868- Robert Millikan
Lived in Morrison, Illinois in 1868
Robert A. Milikan is best known for measuring the charge on the electron.
The oil drop experiment was performed by Robert A. Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron). The experiment entailed observing tiny charged droplets of oil between two horizontal metal electrodes.
An interesting fact about Robert Millikan is that he won the Nobel Prize in Physics in 1923.
"Robert A. Millikan." Biography.com. A&E Networks Television, 02 Apr. 2014. Web. 26 Jan. 2017. <http://www.biography.com/people/robert-a-millikan-9408867#synopsis>.
1879- Albert Einstein
Lived in Wuttemberg, Germany in 1879.
Greatly interested in the atomic view of matter, the young Einstein devised a mathematical method of calculating the size of atoms and molecules in early 1905.
From an analysis of sugar molecules dissolved in water, he calculated both the diameter of the sugar molecule and Avogadro’s number (the number of molecules per unit volume under standard conditions) from the known viscosity of the liquid and the diffusion rate of sugar.
An interesting fact about Einstein is that his great breakthroughs came from visual experiments performed in his head rather than the lab.
"Einstein and Gravitation." The Science News-Letter 67.18 (1955): 275. Web. <https://coraifeartaigh.files.wordpress.com/2008/07/einstein-1.pdf>
1885- Niels Bohr
Lived in Copenhagen, Denmark in 1885.
Niels Bohr came up with the revolutionary theory on atomic structures. He proposed that an electron is found only in circular paths or orbits around the nucleus.
In the model he created, an electrons energy is determined on how far away the energy level is from the nucleus. He also determined how many electrons were allowed on each energy level by giving the energy levels numbers.
An interesting fact about Bohr is that he founded Institute of theoretical physics
"Niels Bohr." Atomic Theory 101. N.p., n.d. Web. 26 Jan. 2017. <http://atomictheory101.weebly.com/niels-bohr.html>.
1887- Erwin Schrodinger
Lived in Vienna, Austria in 1887.
Erwin Schrödinger went on to become a noted theoretical physicist and scholar who came up with a groundbreaking wave equation for electron movements.
The thought experiment proposed a scenario in which a cat was hidden in a sealed box, where the cat's life or death was dependent on the state of a particular sub-atomic particle. According to the Copenhagen interpretation, the cat remains both alive and dead until the box is opened, and it is the act of measurement that causes the calculated set of probabilities in the wave function to “collapse” to the value defined by the measurement.
He was awarded the 1933 Nobel Prize in Physics.
"Erwin Schrödinger." Biography.com. A&E Networks Television, 29 Oct. 2014. Web. 26 Jan. 2017. <http://www.biography.com/people/erwin-schrdinger-9475545>.
1891- James chadwick
Lived in Cheshire, England in 1891.
James Chadwick proved the existence of neutrons. Neutrons were particles that did not contain any charge.
Chadwick's experiment included projecting alpha particles toward Beryllium "the light element". The emitted particles after enduring the Beryllium target (becomes neutrons) and fall on the paraffin wax. The paraffin wax in turn releases another type of particle (protons). At that time atoms were thought to be made up of protons and electrons.
He was knighted and his name became Sir James Chadwick.
"James Chadwick." Atomic Theory 101. N.p., n.d. Web. 26 Jan. 2017. <http://atomictheory101.weebly.com/james-chadwick.html>.
1892- Louis De Broglie
Lived in France in 1892.
Louis de Broglie discovered the "wave nature" of electrons.
Experiments had indicated that the electron must move around a nucleus and that, for reasons then obscure, there are restrictions on its motion.
He also studied atomic energy, cybernetics, gamma rays, optics, particle accelerators, x-rays, and wave-guides.
"Louis De Broglie." Atomic Theory 101. N.p., n.d. Web. 26 Jan. 2017. <http://atomictheory101.weebly.com/louis-de-broglie.html>.
1897- J.J. THomson
Lived in Manchester, England in 1897.
Thomson is credited with discovering electrons and isotopes.
He was the first to suggest that electrons were 1000 times smaller than the actual atom itself. He discovered this through his exploration of cathode rays. His experiments suggested not only that cathode rays were over 1000 times lighter than the hydrogen atom, but also that their mass was the same whatever type of atom they came from.
He came up with the "Plum Pudding" model.
"JJ Thomson." Atomic Theory 101. N.p., n.d. Web. 26 Jan. 2017. <http://atomictheory101.weebly.com/jj-thomson.html>.
1901- Werner heisenberg
Lived in Würzburg, Germany in 1901.
Heisenberg's name will always be associated with his theory of quantum mechanics. This was published in 1925 when he was 23 years old. This is what led him to win the Nobel prize in 1932. This theory was about the radiation emitted by atoms that can be observed. One of his most memorable discoveries is the Uncertainty Principle. He said this means that electrons do NOT travel in neat orbits. Also, all electrons that contain photons will then change momentum and physics.
Instead of focusing mainly on scientific terms, this idea brought mathematics more into understanding the patterns of an atom's electrons. Werner's discovery helped clarify the modern view of the atom because scientists can compare the actually few numbers of atoms there are, by their movements of electrons, and how many electrons an atom contains.
Captured as prisoner by American troops and sent to England.
"Heisenberg." Atomic Theory 101. N.p., n.d. Web. 26 Jan. 2017. <http://atomictheory101.weebly.com/heisenberg.html>.
1911- Ernest Rutherford
Lived in Spring Grove, New Zealand in 1911.
While collaborating with JJ Thomson- Rutherford looked at ion producing radiations. He labeled the two radiations types he found, alpha and beta. Alpha particle resembled the nucleus in a helium atom and the beta particle resembled an electron. He found that when alpha and beta charges were released at the same time they caused a chemical change across atoms.
After experimentation with alpha particles, he made the discovery that "the total mass of an atom is concentrated in the atoms nucleus." After this discovery he paved a path for the "nuclear model, nuclear physics, and the potential atom bombs."
At age 10, he conducted his first science experiment.
"Ernest Rutherford." Atomic Theory 101. N.p., n.d. Web. 26 Jan. 2017. <http://atomictheory101.weebly.com/ernest-rutherford.html>.
1934- Marie Curie
Lived in Old Town Warsaw, Poland in 1934.
Marie Curie worked on radioactivity and in 1898 she reported the possible existence of a new, powerfully radioactive element in pitch blend ores. In other words, elements may change into another element naturally due to unstable nucleus.
Marie discovered that thorium gives off the same rays as uranium. Her continued systematic studies of the various chemical compounds gave the surprising result that the strength of the radiation did not depend on the compound that was being studied. It depended only on the amount of uranium or thorium.
Her discovery of radium and polonium in 1898 won her the Nobel Prize, and changed the course of modern history because it paved the way for building the atomic bomb.
Caldaza, Nikolai. "Marie Curie and The Atomic Theory." Marie Curie and The Atomic Theory. N.p., 01 Jan. 1970. Web. 26 Jan. 2017. <http://nikkibeecalanas.blogspot.com/2012/08/marie-curie-and-atomic-theory_17.html>.