History of atoms timeline- Drayna & Westbrook

DEMITRIUS 500 BC

500

Democritus discovered all of the following:
1.All matter consists of invisible particles called atoms.
2. Atoms are indestructible.
3. Atoms are solid but invisible.
4. Atoms are homogenous.
5. Atoms differ in size, shape, mass, position, and arrangement.

History of the Atom

Period: 500 to Jan 1, 1901

Drayna & Westbrook

LAVOISER

Oct 13, 1744

He found that oxygen plays a role in combustion.

DALTON

Oct 13, 1766

Dalton discovered that elements are made of extremely small particles called atoms. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed. He also discovered that atomsof the same element are identical (which was proved wrong due to isotopes), atoms combine in whole numbers, and atoms are never changed to atoms of another element.

MENDELEEV

Oct 13, 1834

Mendeleev developed the periodic table.

GOLDSTEIN

Oct 13, 1850

Eugen discovered the proton, and that it has more mass than the electron

THOMPSON

Oct 13, 1856

J.J. discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by numerous scientists at the time. His model of the atom was compared to plum pudding.

PLANCK

Oct 13, 1858

Max Planck discovered that energy did not flow steadily, but instead it flowed in discrete packets.

MILLIKAN

Oct 13, 1868

Millikan measured the charge of a single electron (neutral). He determined the mass of an electron, and figured that something must be positive to balance out the negative.

RUTHERFORD

Oct 13, 1871

Rutherford identified alpha particles as helium nuclei. He was known for his gold foil experiment. Most particles blasted through the foil, but some bounced back, or bounces through at angles. He discovered that the nucleus is small, dense, and positive, and that an atom is mostly empty space.

BOHR

Oct 13, 1885

Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory.

SCHRODINGER

Oct 13, 1887

Erwin generated a mathematical model for the distribution of electrons in an atom.

MOSELEY

Oct 13, 1887

Moseley founded that certain lives in the X-ray spectrum of each element moved the same amount each time the atomic number was added to 1.

CHADWICK

Oct 13, 1891

James Chadwick discovered the neutron in 1932.

HEISENBERG

Oct 13, 1901

Heisenberg discovered a way to formulate quantum mechanics in terms of matrices.