Atomic Theory - the History by leslie lopez

In 400 B.C an ancient Greek pre-Socratic philosopher named Democritus atomic theory said that all matter is made up is small indestructible units called atoms.

In 1704 Issac Newton theorized that there were , little small pieces of mass that were swimming everywhere

In 1832 Michael Faraday developed the two laws of electrochemistry, which is a branch of chemistry that deals with relations between electrical and chemical things.

In 1859 J. Plucker built one of the first a high-vacuum tube in which cathode rays produce a luminous image on a fluorescent screen, used chiefly in televisions and computer terminals. A cathode is the negatively charged electrode.

Henri Becquerel discovered radiations from looking at the effects of x-rays on photographic film in 1896

In 1897 J,J. Thomson determined the charge to mass ration of electrons to be e = 1.6021773 x 10 -19 c
M = 9.109390 x 10 -31 kg

Alpha, beta and gamma rays in radiation were discovered in 1898 by Rutherford

The idea of quantization was proposed by Max Planck in 1900 to explain how a hot, glowing object emitted light.

In 1900 Frederick soddy came up with the term "isotope" to explain the unintentional breakdown of radioactive elements. In 1904 Richard Abegg found that inert gases have a stable electron configuration which The highest occupied electron shell is called the valence shell, and the electrons occupying this shell are called valence electrons

Hans Geiger invented a device that could detect alpha particles in 1906. Alpha particles is a helium nucleus emitted by some radioactive substances, originally regarded as a ray.

H.G.J Moseley discovered that the number of protons in an element determines its atomic number in 1914

IN 1922 Niels Bohr proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.

Cockcroft/Walton created the first nuclear reaction, producing alpha particles in 1929

In 1930 Paul Dirac proposed the existence of a subatomic particle having the same mass as a given particle but opposite electric or magnetic properties called antiparticles.

James Chadwick discovered neutrons, particles whose mass was close to that of a proton in 1932

In 1938 Lise meitner, Hahn, and Strassman discovered nuclear fission. A uranium-235 atom absorbs a neutron and fissions into two new atoms, releasing three new neutrons and some binding energy. 2.

From 1941-51 Glenn seaborg discovered 8 transuranium elements

Enrico Fermi created the first man-made nuclear reactor.

]]>