The ATOM: History

Explained

Democritus, an ancient Greek Philosopher living from 460 BC to 370 BC, had the revolutionary idea that matter is composed of tiny particles moving in a void. This was one for the early steps toward the Atomic Theory.

460 BCE

Antoine-Laurent de Lavoisier was a French nobleman and chemist. 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. He was born on August 26, 1743, and died on May 8, 1794.

John Dalton (1766–1844), an Englishman, arrived at his views of atomism by studying meteorology, which was a keen interest of his. Through his observations he established what is now known as “Dalton’s Theory.” This theory states that formed matter is composed of extremely small particles called atoms, atoms are indivisible and indestructible, atoms of a given element are identical in size, mass, and chemical properties, atoms of specific elements are different than those of other elementsin a chemical reaction, and atoms separate, combine and/or rearrange.

1743 A.D.

1766 A.D.

The British physicist Joseph John Thompson, born in 1856 and dying in 1940, discovered the electron via a series of experiments in 1897. He was studying the nature of electric discharge in a high-vacuum cathode-ray tube, and he interpreted the deflection of the rays as evidence of “bodies much smaller than atoms.”

1856 A.D.

New-Zealand born Ernest Rutherford (1871-1937) contributed to the atomic theory by postulating the nuclear structure of the atom. Through experiments he conducted he found that when alpha particles are fired into gas atoms, a few are violently deflected. These results imply a dense, positively charged central region containing most of the atomic mass.

1871

Robert A. Millikan was an American experimental physicist born on March 22, 1868 in Morrison, IL. Millikan was able to measure the charge of an electron with an oil-drop apparatus. By studying individual droplets Millikan showed that the charge on a drop was always some multiple of 1.59 * 10^-19 C. His finding supported Thomson’s findings, as Millikan found that the mass of an electron is at least 1000 times smaller than the lightest atom. He died on December 19, 1953.

1868

Marie Curie, born in 1867 in Poland, helped discover the phenomenon of radioactivity. Before her death in 1934 she was also able to achieve her major objective of producing a pure specimen of radium.

1867

James Chadwick was born October 20, 1891 in Bollington, U.K. He was a Physicist who took note of Frederic and Irene Joliot-Curie (Marie Curie) and their method for tracking particle radiation. Chadwick repeated their experiments but with the goal of looking for a neutral particle -- one with the same mass as a proton, but with zero charge. His experiments were successful as he was able to determine that the neutron did exist and that its mass was about 0.1 percent more than the proton's.

1891

Max Planck , a German theoretical physicist born in Kiel Germany on April 23, 1858 made important observations about energy; he proposed that energy, instead of being continuous, comes in distinct particles, referred to as “quanta.” Planck found that the energy radiated from a heated body is exactly proportional to the wavelength of its radiation. And thus inferred that as temperature increases, energy increases and it's more likely that quanta with higher energy will be radiated.

1858

Albert Einstein (1879-1955) was a German-born theoretical physicist. He developed the general theory of relativity, one of the two pillars of modern physics. Einstein's work is also known for its influence on the philosophy of science. Einstein treated matter and energy as exchangeable, and became famous for the theory of relativity, which laid the basis for the release of atomic energy.

1879

Niels Bohr was a Danish Physicist born on October 7, 1895 and dying on November 18, 1962. He introduced conceptions borrowed from the Quantum Theory established by Planck, and he succeeded in working out and presenting a picture of atomic structure. His version of the atomic structure still largely first today’s explanation of the physical and chemical properties of the elements.

1895

Louise de Broglie was born on August 1892 in Dieppe France. Broglie first introduced the theory of wave mechanics. It offered an explanation to the question of the motion of electrons within the atom.

1892

Erwin Schrodinger, an Austrian physicist born on August 12 1887, added to Bohr’s atom model. He used mathematical equations to describe the likelihood of finding an electron in a certain position; this atomic model is called the quantum mechanical model.

1887

Werner Heisenberg (1901-1976) was a German physicist who developed the “matrix mechanics” which was the formulation of quantum mechanics. It described how the quantum jump occurs and interprets the physical properties of particles as matrices that evolve over time.

The Atomic Theory1901

Work Cited• PBS. "Atom Builder." PBS. PBS, n.d. Web. 09 Oct. 2015.

<http://www.pbs.org/wgbh/aso/tryit/atom/>.

• Lahev, Oren. "History of the Atomic Theory I- Ancient Times." LearnHub. EduComp, n.d. Web. 09 Oct. 2015. <http://chemistry.learnhub.com/lesson/3663-history-of-the-atomic-theory-i-ancient-times>.

• "Homepage of the Chemical Heritage Foundation | Chemical Heritage Foundation." Homepage of the Chemical Heritage Foundation | Chemical Heritage Foundation. Chemical Heritage Foundation, n.d. Web. 09 Oct. 2015. <http://www.chemheritage.org/>.