History of Atom

Democritus (1st to identify possibility of atoms)

500

Created a theory that said matter couldn't be divided into smaller pieces forever; eventually the smallest piece would be obtained
(atomos-indivisible)

John Dalton (father of modern atomic theory)

Aug 1, 1803

-All matter is made of atoms which can't be destroyed/divided.
-All atoms in an element has the same mass & properties.
-Compounds are the combination of two or more different kinds of atoms
-A chemical reaction is the rearrangement of atoms.
-Atoms can't be created or destroyed

Henri Bacquerel

Aug 30, 1896

Discovers chemicals spontaneously decompose

JJ Thomson

Jan 1, 1897

Created plum pudding model. The theory suggests that the atom had smaller parts (protons & electrons). The atom has a sphere where positive protons are surrounded by negative electrons which gives it an overall neutral charge

Marie Curie

Aug 1, 1898

Studied uranium and created the actual saying of "radioactivity."

Robert Millikan

Jan 1, 1909

Used the "oil drop experiment" to measure an electron's charge.

Earnest Rutherford

Mar 7, 1911

Took part in the "gold foil experiment." He also realized that the mass of an atom is at the center in a nucleus, which holds little volume.

Neils Bohr

Jan 1, 1922

Refined Rutherford's model by creating the Bohr's Model. Electrons travel in certain levels. Electrons with low energy are closer to the nucleus; electrons with high energy are farther away from the nucleus.

Louis deBroglie

Jan 1, 1923

Discovered that electrons have properties of waves and particles.

Werner Heinsenberg

Jan 1, 1927

Created the uncertainty principle that states: it's impossible to determine the position and momentum of an electron. He created a "cloud model"

Erwin Schrodinger

Jan 1, 1930

Showed that waves can describe electrons mathematically by using quantum numbers

James Chadwick

Aug 1, 1932

Discovered the neutron.