Atomic Timeline

Atomic Timeline

Period: 460 BCE to 1987

Democritus

370 BCE

Lived 460 BC-370 BC
Born In: Abdera, Greece
Contribution: Theorized the existence of atoms Democritus was among the first to theorize about the atom in a time where atomism was still a debated topic. He explained the phenomena of taste, color, and the different states of matter as variations in an atom's position, shape, and its location relative to the structure formed by it and other atoms.

Antoine Lavoisier

1794

Lived 1743-1794
Born In: Pairs, France
Contribution: Oxygen theory of combustion and Law of conservation of mass Antoine Lavoisier through experimentation aided by Joseph Priestly, isolated air and discovered the element oxygen, which aided in his research of oxidation and the calxes created from metal when exposed with air. Among these experiments included his observation of sulfur gaining weight from air when burned.

John Dalton

1844

Lived 1766-1844
Born In: Eaglesfield, UK
Contribution: Theorized of a new atomic theory, Dalton's Law of Partial Pressures John Dalton was among the first scientists to usher in a more modern take of the atom, in Dalton's case he theorized atoms were building blocks, and the atoms of elements were unique in size and mass to that element. He also created the Law of Partial Pressures after several experiments, including observations of water vapor absorbed by air at varying temperatures.

Marie Curie

1934

Lived 1867-1934
Born In: Warsaw, Poland
Contribution: Discovered Radium and Polonium, Atomic physics Marie Curie's biggest contribution to atomic theory was the work she did regarding uranium rays, and how their condition was constant regardless of the state of the uranium. This brought her to the realization that the rays were brought about via the uranium's atomic structure. She also discovered radium and polonium by isolating them from pitchblende, a material she studied extensively.

Ernest Rutherford

1937

Lived 1871-1937
Born In: Brightwater, New Zealand
Contribution: Created an atomic model Ernest Rutherford postulated the electrons around an atom all orbited the nucleus, which was very small in comparison. He did this via his gold foil experiment, in which he used a radioactive element to shoot targeted particles at gold foil. His revolutionary idea stemmed from the fact only some of the particles went through the foil, as some were deflected. This went against the previous model of atoms.

Sir Joseph John Thomson

1940

Lived 1856-1940
Born In: Manchester, UK
Contribution: Discovered the electron Sir Joseph Thomoson discovered the electron through experimentation with cathode rays, which he discovered were negatively charged after improving upon an experiment done by Heinrich Hertz who was spurred by the discovery of a ray found in a certain glass vacuum. At the time, the accepted models of atoms did not account for charges, and as a result Joseph founded the electron .

Max Planck

1947

Lived 1858-1947
Born In: Kiel, Germany
Contribution: Contributed to Quantum Theory, Planck's Constant Max discovered the energy of each quantum is equal to the frequency of the radiation multiplied by a universal constant. This is known as Planck's Constant, which was derived from his study of the distribution of radiation from blackbodies, which were materials that could absorb radiant energy.

Robert Millikan

1953

Lived 1868-1953
Born In: Morrison, Illinois
Contribution: Quantified the charge of electrons Through his oil drop experiment, Robert Millikan was able to quantiofy the charge of electrons by suspending drops of oil between two metal electrodes. They did this by balancing the downward gravitational force with the electric forces of the electrodes.

Albert Einstein

1955

Lived 1879-1955
Born In: Ulm, Germany
Contribution: Theory of relativity The most pertinent contributions of Albert Einstein were his theory of relativity, which stemmed from his mathematical work in coordination with Marcel Grossman, who introduced Einstein to some of the principles he would use to formulate the theory of relativity using statistics and probability regarding the bending of light.

Erwin Shrodinger

1961

Lived 1887-1961
Born In: Vienna, Austria
Contribution: Provided equations to calculate the probability of the location of electrons, electron cloud Erwin built on the atomic models of the past and proposed the existence of the electron cloud, which would account for the wave-like nature of electrons and elaborate on the Bohr model to help explain the different levels of electron waves. He also developed calculations for the probability of an electron to be in a location and its energy level

Niels Bohr

1962

Lived 1885-1962
Born In: Copenhagen, Denmark
Contribution: Proposed a model of an atom in which electrons could only orbit in particular places around the nucleus Niels Bohr falsely adjusted the Rutherford model to account for the different energy levels of electrons, he stated that electrons had fixed orbits, and to switch orbits electrons had to lose or gain charge, releasing radiation in the process. He theorized this because of the idea that an electron could not lose more than n = 1 energy

James Chadwick

1974

Lived 1891-1974
Born In: Bollington, UK
Contribution: Discovered Neutron By shooting Beryllium with alpha particles from the decay of polonium, James was able to create radiation that could pervade through lead, which was deemed impossible at the time. This discovery led him to theorize about a different particle, neutrons, which functioned in conjunction with electrons inside the atom.

Werner Heisenberg

1976

Lived 1901-1976
Born In: Wurzburg, Germany
Contribution: Uncertainty principle Werner's thought experiments regarding how particles are measured using different apparatuses led him to the conclusion that it was theoretically impossible to produce any exact quality of the universe, as the measuring instruments used would disrupt the measurement. Such as the way light and radiation disrupt the momentum and position of electrons.

Louis De Broglie

1987

Lived 1892-1987
Born In: Dieppe, France
Contribution: Theorized the existence of atomic waves Louis discovered the existence of atomic waves by observing the way electron beams were reflected in crystals and then spread through metal foil. This explained why the movement for electrons around the nucleus were somewhat restrained, as atomic waves created unseen barriers between certain pathways in the atom.