History of Atoms

Democritus

460

Born: 460 BC
Died: 370 BC
Field: Philosophy (philosopher means that his discoveries were not experimental based)
Famous For: Formulation of an Atomic Theory of the Universe
Democritus was the first person to even suggest the thought of an atom existing, however they don’t have actual evidence on the time period. He was most known for stating the resemblance of an atom, being indivisible and indestructible. This was later switched in multiple ways but it still marks a huge discovery.

Robert Boyle

Jan 25, 1627

Born: January 25th, 1627
Died: December 31st, 1691
Field: Physics and Chemistry
Famous For: Boyle’s Law and founder of modern chemistry
Boyle’s best known for his own law, discovered in 1662, which is a law that describes the inversely proportional relationship between the pressure and volume of a gas, if the temperature is held constant. He is considered the founder of modern chemistry because he is the first modern chemist to date.

Antoine Lavoiser

Aug 26, 1743

Born: August 26th, 1743
Died: May 8th, 1794
Field: Chemistry and Biology
Famous For: Recognizing Oxygen & Hydrogen, Oxygens role in combustion, Helped construct the metric system, and wrote the first extensive list of elements.
Lavoisier is known for a few different things, in 1778 he recognized oxygen and its role that it played in combustion (a high heat/temperature chemical reaction between a fuel and oxygen) as well as discovering hydrogen in 1783.

John Dalton

Sep 6, 1766

Born: September 6th, 1766
Died: July 27th, 1844
Field: Chemistry, Meteorology, and Physics
Famous For: Developing the Modern Atomic Theory
“If two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be the ratios of small whole numbers.”
It was in 1803 that John Dalton made his theory. Between all this data and experiments, he stated a simple belief that matter exists as atoms.

Dmitri Mendeleev

Feb 8, 1834

Born: February 8th, 1834
Died: February 2nd, 1907
Field: Chemistry and Physics
Famous For: Formulating the Periodic Law and created a Periodic Table of Elements
Although the Periodic Table of Elements was already created, Mendeleev created a new and improved version in 1869 to correct the mistakes of former creators and add additional information.

Eugene Goldstein

Sep 5, 1850

Born: September 5th, 1850
Died: December 25th, 1930
Field: Physics
Famous For: Discovery of anode rays & the proton
Eugene Goldstein is most known for his discovery of the proton in 1917. He is also known for discovering anode rays which concluded that because of positive and negative charges the cathode rays could travel from the anode to the cathode.

JJ Thomson

Dec 18, 1856

Born: December 18th, 1856
Died: August 30th, 1940
Field: Physics
Famous For: Discovering the electron
It wasn’t until 1897 till Thomson discovered the electron while doing an experiment that showed that cathode rays (electron beam) were made up of a negatively charged particle. This also marked the discovery of the first subatomic particle. Although this was what he was most famous for, he was also known as the mad to find the first evidence for isotopes.

Max Planck

Apr 23, 1858

Born: April 23rd, 1858
Died: October 4th, 1947
Field: Physics
Famous For: The quantum theory of energy
Planck is best known for coming up with the quantum theory of energy in 1900 which has to do with the understanding of atomic and subatomic particle processes. Although this was his main accomplishment he also contributed multiple times to theoretical physics.

Robert Millikan

Mar 22, 1868

Born: March 22nd, 1868
Died: December 19th, 1953
Field: Physics
Famous For: Discovering the mass and charge of electrons
Used the “All Drop experiment” in 1923 to determine the mass and charges of electrons. Its now known that an electron is 1/1840 to the mass of a proton because of Robert Millikan's discoveries.

Ernest Rutherford

Aug 30, 1871

Born: August 30th, 1871
Died: October 19th, 1937
Field: Physics
Famous For: Gold Foil experiment, First to split the atom, and his theory of atomic structure
Rutherford is most known for his Gold Foil experiment in 1911 which showed the evidence; that most particles passed through the foil, a few of the particles were deflected, and very few were greatly deflected. This experiment was done to show the splitting of an atom, and later it lead to the development of the atomic structure theory.

Niels Bohr

Oct 7, 1885

Born: October 7th, 1885
Died: November 18th, 1962 (age 77)
Field of Study: Physics
Famous For: Developed the model of the atom
This model was introduced in 1913. This model represents the hydrogen atom as a small and positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus. Similar in structure to the solar system, but instead of gravity as its “pulling force” it uses electrostatic forces.

Erwin Schrondinger

Aug 12, 1887

Born: August 12th, 1887
Died: January 4th, 1961
Field: Physics
Famous For: Discovered the electron cloud
In 1926, Schrodinger took the Bohr atom model one step further into experiments and used mathematical equations to describe the probability of finding certain electrons in specific positions. (the quantum mechanical model)

Henry Moseley

Nov 23, 1887

Born: November 23rd, 1887
Died: August 10th, 1915
Field: Physics and Chemistry
Famous For: His establishment of the Periodic Table of the Elements
Moseley based the Periodic Table of of the chemical elements in 1913 found in each element and the order of each of their atomic numbers. This was a huge impact to the scientific world because it was extremely useful, considering we still use it today.

James Chadwick

Oct 20, 1891

Born: October 20th, 1891
Died: July 24th, 1974
Field: Physics & Radioactivity
Famous For: Discovery of the neutron
James discovered the neutron in 1932, when he was scattering data to calculate the mass of his neutral particle. As they studied atomic disintegration they noticed that the atomic number was less than the atomic mass. Keeping this problem in mind, experiments being done around the world caught his eye. In conclusion of the experiments, the neutron did exist.