Atomic Timeline

Events

Democritus

220 BC

He give the name to the atom

issac newton

1704

Proposed a mechanical universe with small solid mass in motion

Jhon Dalton

1803

Proposed an atomic theory with spherical solid masses in motion

Michael Faraday

1832

Study the effect of electricity on solutions

Dimitri Mendeleev

1869

Arranges elements in 7 groups.He discovered that the properties of element were periodic functions of their atoms weigh

Sir Williams Crookes

1879

He investigated the properties of cathode rays, showing that they travel in straight lines, cause fluorescence when they fall on some substances, and that their impact can produce great heat.

G.J Stoney

1894

Proposed that electricity was made of discrete negative particles called electrons

Wilhelm Roentgen

1895

Was the first person to discover electromagnetic radiation in a wavelength range commonly known as X-rays today.

J.J Thompson

1897

Discovered the electron.He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas.

Max Planck

1900

Used the idea of quanta(discrete units of energy) to explain hot glowing matter

Hans Heiger

1906

Developed an electrical device to click when hit with alpha particles

R.A Millikan

1909

Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron.

Ernest Rutherford

1911

He carried out the Geiger–Marsden experiment, which demonstrated the nuclear nature of atoms by deflecting alpha particles passing through a thin gold foil.

HGJ Moseley

1914

Using x-ray tubes, determined the charges on the nuclei of most atoms.

Niels Bohr

1922

He proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another.

Louis de Broglie

1923

Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality.

Werner Heisenberg

1927

:Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminacy - you can not know both the position and velocity of a particle.

Erwin Schrodinger(

1930

Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom.

James Chadwick

1932

Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron.

Enrico Fermi

1942

Conducted the first controlled chain reaction releasing energy from the atoms nucleus.