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John Dalton
He proposed the Atomic Theory in 1803 which stated that (1) all matter was composed of small indivisible particles termed atoms, (2) atoms of a given element possess unique characteristics and weight, and (3) three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules) -
Michael Faraday
Faraday discovered electromagnetic induction, the principle behind the electric transformer and generator. This discovery was crucial in allowing electricity to be transformed from a curiosity into a powerful new technology. -
E. Goldstein
He used cathode ray tubes to discover that canal rays have opposite properties of electrons. -
Dmitri Mendeleev
Mendeleev is best known for his work on the periodic table; arranging the 63 known elements into a Periodic Table based on atomic mass.He predicted the existence and properties of new elements and pointed out accepted atomic weights that were in error -
Sir William Crookes
Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. -
J.J. Thomson
Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram. Studied "canal rays" and found they were associated with the proton H + -
Marie Sklodowska Curie
Cury announced the discovery of a new chemical element, polonium. At the end of the year, they announced the discovery of another, radium. Her discoveries with her husband added on to the periodic table. -
Ernest Rutherford
Created the Rutherford Model by using alpha particles as atomic bullets, probed the atoms in a piece of thin gold foil . He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus. -
Niels Bohr
He advanced the theory of electrons travelling in orbits around the atom's nucleus, with the chemical properties of each element being largely determined by the number of electrons in the outer orbits of its atoms. He developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete, and that they revolve in stable orbits around the atomic nucleus, but can jump from one energy level to another. -
Henry Moseley
Measured the X-Ray spectra of some elements and 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. He wrote"The atomic number of an element is equal to the number of protons in the nucleus" called Moseley's law. -
Louis de Broglie
He proposed that all moving particles — particularly subatomic particles such as electrons — exhibit a degree of wave-like behavior. -
Erwin Schrodinger
He explored whether or not the movement of an electron in an atom could be better explained as a wave rather than as a particle. Schrodinger's equation describes an electron as a wavefunction instead of as a point particle. -
Werner Heisenburg
It is mathematically impossible to simultaneously derive the position and momentum of an electron known as the Heisenberg uncertainty principle. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle. -
Paul Dirac
He formulated the Dirac equation, which describes the behaviour of fermions and predicted the existence of antimatter.He discovered the anti-electron (positron). -
James Chadwick
He exposed various elements, such as hydrogen and nitrogen, to the mysterious "beryllium radiation", and by measuring the energies of the recoiling charged particles, he deduced that the radiation was actually composed of electrically neutral particles which could not be massless like the gamma ray, but instead were required to have a mass similar to that of a proton. He discovered the neutron.
