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democritus
he came up with the idea that matter consisted of tiny particles called atom. he also created the first atom model which was just a solid ball and also has a theory that states “The universe is composed of two elements: the atoms and the void in which they exist and move.” -
Lavoisier
provided the formula for the conservation of matter in chemical reactions, and also distinguished between an element and a compound. -
john dalton
Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. Dalton made his most important contribution to science called the atomic theory. The theory consists that matter is composed of atoms of differing weights and combine in simple ratio’s by weight. Dalton was the first to prepare a table of relative atomic weights. -
JJ thomson
thomsom discovered the electron. he strengthened the theory of positively charged particles in atoms. he siad that since atoms hadnegaive charged particles there had to be positive charged particles. he envisoned the atoms being mostly positive matter, with the negative pieces sprinkled in. used cathode ray to find out the negativ. -
henry becquerel
While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays. this added radioactivity to the model -
the curies
Pierre and Marie Curie are best known for their work in the study of radioactivity, which led to their discovery in 1898 of the elements radium and polonium.Pierre Curie and his wife Marie Curie stated that radioactive materials cause atoms to break down spontaneously, releasing radiation in the form of energy and subatomic particles -
rutherford
he proved that there are positive electronsin the core of the atom so it gave the atom a positive charge.he directed a narrow beam of alpha particles at a very thin sheet of gold foil. also said that all the mass is cocentrated in the nucleus and the atom is mostly empty spcace -
robert millikan
Determined unit charge of the electron with his oil drop experiment in 1909. This allowed calculation of the mass of electrons and positively charged atoms. this work added to the work to jj thomson who discovered the electron -
mosley
logical way of puttig the periodic table together .His main contributions to science were the quantitative justification of the previously empirical concept of atomic number, and Moseley's law. -
max planckt
he developed the quantum theory. this showed that atoms moved and do not just stay in one place. they move in wave pattern. this tells us more about what it does. this also helped many other scientists to help describe the qualties of the atom -
neil bohr
He passed on to a study of the structure of atoms based on Rutherford's discovery of the atomic nucleus, proposed arent on any random orbit rather they are on a special orbit. he came up with concept called quantum mechanics or quantized energy. he also modeled the atom after our solar sytem -
werner heisenberg
Heisenberg is known for his Uncertainty Principle which states the the exact location and energy of an electron cannot be determined simultaneously. Finding one value (the energy or the location), means that there will be some uncertainty when finding the other value. -
erwin schrondinger
Schroedinger explained movement of an electron in an atom as a wave.Edwin Schrodinger stated that rather than electrons being distributed within an electron configuration of shells and energy levels, they were arranged in orbitals which were systematically distributed within Electron Clouds. He defined an orbital as: The region of space that surrounds a nucleus in which two electrons may randomly move. -
james chadwick
In 1932, James Chadwick discovered the neutron,He established that atomic number is determined by the numbers of protons in an atom.when beryllium was bombarded with positively charged alpha particles a beam with a high penetrating power was created. James Chadwick discoverd that this beam was not deflected by either electric or magnetic fields, meaning it contained neutral particles- neutrons.so it added neutrons to the model -
aristotle
he had an idea that life was made up of earth wind fire and water, He didn't think atoms could be in constant motion in a void.Aristotle disbelieved the ancient Greek theory of atoms being of different sizes, regular geometric shapes and being in constant motion. there were also four qualities to his theory dryness, hotness, coldness, and moistness.
