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John Dalton
He proposed the Law of Multiple Proportions. This led directly to the making of the Atomic Theory. He proposed a system of symbols to represent atoms of different elements. He recognized the existence of atoms of elements. He also found that five percent of the male population and less than one-tenth percent of the female population was colour blind. -
J.J Thompson
He was able to identify the existence of electrons in an atom. The meant that atoms are not invisible and could be seen. His theory also suggested that atoms where spherical and had a positive charge. Thomson discovered the electron in the year 1897. His work put forward a new theory, that atom was made up of small particles. Thus he discovered the electrons. He proved his theory using the cathode ray tube. -
Marie Curie
Curie was known for shifting scientific opinion from the idea that the atom was solid and indivisible to an understanding of subatomic particles. One important point was that radioactivity showed that the atom was divisible. This was significant as up to that time, from Dalton's theory, atoms were thought to be indivisible. Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium & radium. -
Ernest Rutherford
He proposed the nuclear atom as the result of the gold-foil experiment. Also in 1920, Ernest proposed the existence of the third atomic particle, the neutron. He proposed that all of the positive charge and the mass of the atom occupied a small space at the center of the atom and that most of the volume of the atom was empty space occupied by the electrons. -
Henry Moseley
Henry Moseley, a british chemist, studied with Ernest Rutherford and developed the application of X-ray spectra to study atomic structure; Moseley's discoveries resulted in a more accurate positioning of elements in the Periodic Table by closer determination of atomic numbers. He discovered that the energy of x-rays emitted by the elements increased in a linear fashion with each successive element in the periodic table. -
Francis Aston
He was the first person to observe isotopes. For example he found that there were three different kinds of hydrogen atoms. While most of the atoms had a mass number of 1 he found hydrogen atoms with mass numbers of 2 and 3. He found definite evidence for the existence of two isotopes of the inert gas neon. -
Niels Bohr
He developed an explanation of atomic structure that shows regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons. The Bohr model was based on his observations of the atomic emissions spectrum of the hydrogen atom. When white light is diffracted with a prism, all the colors of the visible spectrum can be seen. -
Erwin Shrodinger
He developed a powerful model of the atom. The advantage of this model is that it consists of mathematical equations known as wave functions that reach the requirements placed on the behavior of electrons. Erwin Schrodinger used mathematical equations to describe the likelihood of finding an electron in a certain position This atomic model is known as the quantum mechanical model of the atom. This atomic theory predicts the odds of the location of the electron. -
James Chadwick
James predicted the atom would have a neutron. He established that atomic number is determined by the numbers of protons in an atom.He discovered the fourth subatomic particle, the neutron.James Chadwick discoverd that a beam of light was not deflected by either electric or magnetic fields, meaning it contained neutral particles- neutrons. Neutrons were found to have the same mass as protons which accounted for more of the mass of the atom and allowed the masses to match. -
Murray Gell-Mann
He showed scientists what makes up protons and neutrons, quarks. He explained why some hadrons decay rapidly by the strong nuclear force while others decay more slowly by the weak force.He proposed a new classification system for baryons to explain the complicated kinds of particles in collisions.
