History of the Atom



460 BC - 370 BC

He was born in Abdera, Greece. His mentor, Leucippus, originally came up with the atomic theory, but it was then adopted by Democritus. The atomic theory stated that “The universe is composed of two elements: the atoms and the void in which they exist and move.” According to Democritus atoms were miniscule quantities of matter. Democritus hypothesized that atoms cannot be destroyed, differ in size, shape and temperature, are always moving, and are invisible. He believed that there are an infinite number of atoms. This hypothesis was created in 465BC. He published over 70 books.
Born to a family of wealth. Democritus had no technology available to him and did not conduct any experiments to test his ideas. He had no proof that atoms existed and no evidence to back up his claims. He left it to later scientists to prove or disprove his ideas.

Antoine Lavoisier

1743 - 1794

He was from France. He was known for his experimentation skills. One of his favorite experiments being 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. Matter rearranged, but never disappeared. In experiments with phosphorus and sulfur, both of which burned readily, Lavoisier showed that they gained weight by combining with air. With lead calx, he was able to capture a large amount of air that was liberated when the calx was heated.
He was a French nobleman who is considered to this day to be the father of modern chemistry. His work was crucial in a period of discovery that is now known as the Chemical Revolution, or even the First Chemical Revolution.

John Dalton

1776 - 1844

He is from Cumberland, England. His atomic theory said that elements consisted of tiny particles called atoms. It states an element is one of a kind (aka pure) because all atoms of an element are identical. All the atoms that make up the element have the same mass. All elements are different from each other due to differing masses. He experiments with gases that first became possible at the turn of the nineteenth century led John Dalton in 1803 to propose a modern theory of the atom based on the following assumptions. When John Dalton died, 40,000 people attended his funeral procession.
He discovered color blindness, and still today it is sometimes referred to as "Daltonism".

Max Planck

1858 - 1947

He was from Keil, He worked in thermodynamics and led to the formulations of his quantum theory. To explain the colors of hot glowing matter, he said that “energy is radiated in very minute and discrete quantized amounts or packets, rather than in a continuous unbroken wave”. Planck called the packets of energy quanta and he was able to determine that the energy of each quantum is equal to the frequency of the radiation multiplied by a universal constant that he derived, now known as Planck's constant. It is used to describe the behavior of particles and waves at the atomic scale. Planck announced his findings in 1900, and in 1905, Albert Einstein used Planck's quantum theory to describe the particle properties of light. Einstein demonstrated that electromagnetic radiation, including light, has the characteristics of both a wave and, consistent with Planck's theory, a particle. These particles were later called photons. In 1913, Niels Bohr used Planck's theories to develop a new and more accurate model of the atom. Planck made significant contributions to science throughout his life.

Marie Curie

1867 - 1934

She was born in Warsaw, Poland. She traveled to Paris to continue her studies in getting her Licentiateship in Physics and Mathematical Sciences at the Sorbonne. In 1894 she met Pierre Curie, her husband, who was the Professor in the School of Physics. Pierre was the head of the Physics Laboratory at the Sorbonne. In 1903, Marie obtained her Science degree and three years later her husband Pierre died, leaving her the position of professor of General physics. This was the first time a woman had held this position. In 1914, Curie was appointed Director of the Curie Laboratory in the Radium Institute of the University of Paris. Here, Marie developed methods to separate radium from radioactive resides. This allowed careful study of the characterization. It was used for therapeutic properties. President Hoover gave her a grant of $50,000 to purchase radium. She was also a member of the Conseil du Physique Solvay at this time until 1922. She received many awards and honors for her scientific ideas and discoveries. Including two Nobel Prizes, Davy Medal of Royal Society, and her daughter won the Nobel Prize in 1935, being the first mother and daughter to share the honor. She was the author of Recherches sur les Substances Radioactivies in 1904, L’lsotopie et les Elements Isotopes and Traite de Radioactivite in 1910. Her awards were won and papers were written on how she isolated one-tenth of a gram of pure radium chloride from eight tons of pitchblende residue. This required much physical labor. She also determined the atomic weight of radium to be 225. Marie Curie died in Savoy, France, after a short illness, on July 4, 1934. She is referred to as the “mother of atomic physics" and is a legend of the twentieth century science. We now know that radium is toxic and should not be handled. However, it is used to fight cancer and in other forms of medicine.

Robert Millikan

1868 - 1953

He was from Morrison, IL. Robert Millikan contributed to the atomic theory in his own way. Using Thomson’s electron results, he conducted his own experiment, which he called the oil drop method. By conclusion, Millikan confirmed Thomson’s theory.

Ernest Rutherford

1871 - 1937

He was from Brightwater, New Zealand. Ernest Rutherford described the atom as having a central positive nucleus surrounded by negative orbiting electrons. This conclusion was gathered from using the gold and foil experiment, which involved the firing and radioactive particles through thin metal foils and espying them by using screens coated with zinc sulfide. He found out that although most of the particles passed through the foil, 1 in 8000 bounced off, which lead him to the theory that most of the atom was made up of empty space.

Albert Einstein

1879 - 1955

He was born in Ulm, Germany, Using Brownian motion, Einstein was able to accurately calculate the average distance an immersed visible particle would travel in a given time. His mathematic laws governing the movements of invisible particles could be tested and measured by observing the motion of the visible simply using a microscope and a stopwatch. Although this was a very difficult to test a hundred years ago, eventually Einstein’s calculations were fully confirmed by Jean Perrin in 1909, winning Perrin the Nobel Prize.

Niels Bohr

1884 - 1962

He is from Copenhagen, Denmark. Niels Bohr added onto Rutherford’s theory with his own model. His interpretation was that electrons orbited the nucleus of an atom in pre-defined energy levels, and if the energy level was dropped, they would emit a photon. This is how the basis of quantum theory was formed

Erwin Schrodinger

1887 - 1961

He is from Vienna, Austria. Erwin Schrodinger built onto Bohr’s model of the atom with the electron Cloud Model. Of which interpreted the floating motion of the electrons, instead of having a set path for them to travel. He figured the likelihood of the location of the electrons in atoms. According to Schrodinger, Orbitals are areas of space around the nucleus in an atom.

James Chadwick

1891 - 1974

He was born in Bollington, England. Rutherford, Chadwick, and some others believed in the possibility that particles with no charge could be in the nucleus.
In his spare time, through the 1920s, Chadwick made a variety of attempts in the laboratory to find these neutral particles, but without success. He was, however, increasingly convinced in the existence of a neutral particle – the neutron. He couldn’t, however, get the evidence he needed to prove its existence. Then, at the beginning of 1932, Chadwick learned of work that Frederic and Irene Joliot-Curie had just done in Paris. The Joliot-Curies believed they had managed to eject protons from a sample of wax using gamma rays. This did not make sense to Chadwick, who thought gamma rays were not powerful enough to do this. However, the evidence that protons had been hit with sufficient energy to eject them was convincing. The gamma ray source had been the radioactive element polonium. Chadwick drew the conclusion that the protons had actually been hit by the particle he was looking for: the neutron. Feverishly, he began working in the Cavendish laboratory. Using polonium as a source of (what he believed were) neutrons, he bombarded wax. Protons were released by the wax and Chadwick made measurements of the protons’ behavior. The protons behaved in exactly the manner they ought to if they had been hit by electrically neutral particles with a mass similar to the proton. Chadwick had discovered the neutron. Within two weeks he had written to the prestigious science journal Nature to announce the Possible Existence of a Neutron.

Louis De Broglie

1892 - 1987

Louis de Broglie was born in Dieppe, France. His ideas were a basis for developing the wave mechanics theory. This theory has greatly improved our knowledge of the physical nature on the atomic scale. He received the Nobel Prize for Physics on his wave nature of electrons discovery in 1929. He believed that electrons can act like both particles and waves, just like light. He also said that waves produced by electrons contained in the orbit around the nucleus, set up a standing wave of a certain energy, frequency, and wavelength. He discovered that electrons can act like waves which helped explain some of the things electrons do that we had never been able to explain before. Today, quantum physics is applied in lasers, computers, and microscopes.

J. J. Thomson

1897 - 1940

He was born in Cheetham Hill. Thomson was interested in atomic structure, which was evident in his book Treatise on the Motion of Vortex Rings which he won the Adams Prize for in 1884. Joseph returned to America in 1904 and delivered six lectures about electricity and matter at Yale University. He later discovered a method used to separate different kinds of atoms and molecules from the use of positive rays. This idea was developed by Aston, Dempster, and a few other people. Thomson was elected Fellow of the Royal Society in 1884. He served as President from 1916-1920. Also, he received the Royal Medal and Hughes Medal in 1894 and 1902 and many other medals. Thomson studied in Great Britain and also in America. J.J. Thomson discovered electrons and noticed that an atom can be divided. Also, he concluded atoms are made of positive cores and negatively charged particles within it. He developed the Plum Pudding Model before the atomic nucleus was discovered. This model shows that the electrons are surrounded by a "pudding" of positive charges to balance the negative charges. Today, J.J. Thomson's discoveries have helped people to have a better understanding of the atom and its generic makeup.

Werner Heisenberg

1901 - 1976

He is from Wurzburg, Germany. 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.

Werner's contribution to the atomic theory was that he calculated the behavior of electrons, and subatomic particles that also make up an atom. 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. Surrounding the outside of an atomic nucleus is an electron cloud, which is a name given to the electrons that are widely spreading and moving around. In conclusion, Werner Heisenberg contributed to the atomic theory by including quantum mechanics, the branch of mechanics, based on quantum theory, used for interpretating the behavior of elementary particles and atoms. He died of cancer, and he attended the university of Munich.