Final Timeline - Timeline

Democritus’ atomic theory posited that all matter is made up small indestructible units he called atoms

Aristotle no matter how many times you cut the same matter in half you would have the same matter just in pieces

Robert Boyle’s law describes the relationship between absolute pressure and volume of gas

Isaac Newton theorized a mechanical universe with small, solid masses in motion

Antoine Lavoisier proposed the combustion theory which was based on sound mass measurements

Joseph Priestly discovered oxygen

Johann Becher and Georg Stahl came up with the Phlogistic theory

LaVoisier Law of Conservation of Mass: matter can not be created or destroyed

Protus came up with the law of definite proportions

John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.

Joseph Gay-Lussac announced the law of combining volume

Amedeo Avogadro equals volume of gases, under the same conditions have different masses

Michael Faraday developed the two laws of electrochemistry

J. Plucker built one of the first cathode-ray tubes.

Dmitri Mendeleev created the periodic table.

Alfred Nobel invents dynamite

James Clerk Maxwell proposed the theory of electromagnetism and made the connection between light and electromagnetic waves.

G.J. Stoney theorized that electricity was comprised of negative particles he called electrons.

Sir William Crookes’ experiments with cathode-ray tubes led him to confirm the work of earlier scientists by definitively demonstrating that cathode-rays have a negative charge.

E. Goldstein discovered canal rays, which have a positive charge equal to an electron.

G.J. Stoney proposed that electricity was made from electrons

Wilhelm Roentgen discovered x-rays.

Henri Becquerel discovered radiation by studying the effects of x-rays on photographic film.

J.J. Thomson determined the charge to mass ratio of electrons.

J.J. Thomson studied “canal rays” and found they were associated with the proton H +

Rutherford discovered alpha, beta, and gamma rays in radiation.

Marie Sklodowska Curie discovered radium and polonium and coined the term radioactivity after studying the decay process of uranium and thorium.

Max Planck proposed the idea of quantization to explain how a hot, glowing object emitted light.

Frederick Soddy came up with the term "isotope" to explain the unintentional breakdown of radioactive elements.

Hantaro Nagaoka proposed an atomic model called the Saturnian Model to describe the structure of an atom.

Richard Abegg found that inert gases have a “stable electron configuration.”

Albert Einstein published famous equation “e=mc2 “

Hans Geiger invented a device that could detect alpha particles.

R.A. Millikan oil drop experiment that determined the charge and mass of electrons

Philipp Lenard he described atoms as mainly empty space with fast moving particles

Ernest Rutherford used the alpha particles as atomic bullets

H.G.J. Moseley discovered that the number of protons in an element determines its atomic number.

Francis William Aston used a mass spectrograph to identify 212 isotopes.

Niels Bohr proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.

Louis de Broglie proposed that electrons have a wave/particle duality

Robert Goddard experimented with liquid-filled rockets

Heisenberg described atoms as a use of formula connected to the frequencies of spectral lines, proposed Principle of Indeterminacy- you can not know both the position of a particle or the velocity of the same particle

Cockcroft / Walton created the first nuclear reaction, producing alpha particles

Paul Dirac proposed the existence of antiparticles.

Schrodinger viewed electrons as continuous clouds and introduced “wave mechanics” as a mathematical model of an atom

James Chadwick discovered neutrons, particles whose mass was close to that of a proton.

Chien-shiung Wu conducted research on radiation conduction.

Lise Meitner, Hahn, Strassmann discovered nuclear fission.

Between 1941-51 Glenn Seaborg discovered eight transuranium elements.

Enrico Fermi created the first man-made nuclear reactor.