CHEM TIMELINE

DEMOCRITUS

• 460 B.C. - 370 B.C.
• Said all matter consist of atoms.
• Atoms can't be destroyed.
• Solid, but invisible.
• Differ in size, shape, mass, posistion and arrangment.

ANTOINE 1743-1794

• Helped construct the metric system.
• Created the oxygen theory of combustion.

JOHN DALTON 1766-1844

• Created Dalton's atomic theory.
• Made theory at 1805.

LAW OF CONSERVATION OF MASS

• 1789
• States any system closed to all transfers of matter and energy-
• -the mass of the system must remain the same.

DALTON'S ATOMIC THEORY 1805

• One compound was made of two-
• - or more types of atoms with one of each.

J.J. TOMSON 1856-1940

• Created the plum pudding model.

ROBERT MILLIKAN 1868-1953

• Famous for his oil drop experiment.
• Tested the charge of electrons.

PLUM PUDDING MODEL 1904

• Suggest that the atom was a sphere positivley charged with-
• -electrons positioned around it.

CATHODE RAY TUBE 1897

• Was made by Karl Ferdinand Braun.

DIMITRI MENDELEEV 1834-1907

• Formulated the Periodic Law.
• Created his own version of the periodic table.
• Predicted the properties of eight elements that were undiscovered.

NIELS BOHR 1885-1962

• Developed the Bohr Model.
• Said energy levels are discrete.
• Atoms orbit the nucleus in stable orbits.

RUTHERFORD 1871-1937

• Made the Rutherford model.
• Suggest that an atom has a high central charge.
• It's concentrated in a small volume.
• He also discovered the concept of half-life.

ERWIN SCHRODINGER 1887-1961

• Author of many fields inclduing:
• Physics, statistical mechanics, thermodynamics,
• Physics of dielectrics, colour theory and more.

JAMES CHADWICK 1891-1974

• Discovered the nuetron in 1932

HENRY MOSELEY 1887-1915

• Moseley discovered a systematic mathematical relationship between-
• the wavelengths of the X-rays produced and the atomic numbers of the-
• metals that were used as the targets in X-ray tubes.
• This has become known as Moseley's law.

RUTHEFORD MODEL

• Was created in 1911

BOHR MODEL

• Created in 1913
• Was based off of Rutheford's model
• Suggested that atoms had chemical properties

GOLD FOIL EXPERIMENT 1899

• Is commonly call Ruthefords experiment
• Concluded that only a small portion of the atom-
• is positively charged

QUANTUM MECHANICAL MODEL 1925

• The quantum mechanical model is based on quantum theory
• According to quantum theory, it’s impossible to know the exact position
• and momentum of an electron at the same time.

ELECTRON CLOUD MODEL 1925

• Electron cloud is a term used to describe where electrons are when-
• they go around the nucleus of an atom.
• Erwin Schrödinger and Werner Heisenberg created the model.