-
John Dalton
He proposed the theory that matter consists of indivisible particles called atoms and that atoms of a given element are all identical and can neither be created nor destroyed. Compounds are formed by combination of atoms in simple ratios to give compound atoms (molecules). The theory was the basis of modern chemistry. -
William Crooke
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
discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by numerous scientists at the time.In 1904 Thomson suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces. -
Ernest Rutherford
This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space. Rutherford came to this conclusion following the results of his famous gold foil experiment. This experiment involved the firing of radioactive particles through minutely thin metal gold foils and detecting them using screens coated with zinc sulfide, he concluded most of the atom was empty space. -
Quantum Mechanical Model
After Max Planck determined that energy is released and absorbed by atoms in certain fixed amounts known as quanta, Albert Einstein took his work a step further, determining that radiant energy is also quantized—he called the discrete energy packets photons. Einstein’s theory was that electromagnetic radiation has characteristics of both a wave and a stream of particles. -
Niels Bohr
Bohr's greatest contribution to modern physics was the atomic model. The Bohr model shows the atom as a small, positively charged nucleus surrounded by orbiting electrons.Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer -
James Chadwick
Chadwick made a fundamental discovery in the doorman of nuclear science. He proved the existence of neutrons. James predicted the atom would have a neutron. He established that atomic number is determined by the numbers of protons in an atom. He also discovered the fourth subatomic particle, the neutron.
