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300
Aristotle
Aristotle's beliefs contradicted those of his era when it came to atoms. he believed that all matter consisted of four elements (fire, water, earth, air) and that there were four qualities to these elements (dryness, hotness, coldness, moistness). -
460
Democritus
Democritus is credited with inventing the idea of the atom, naming it even. This goes back to his theory with the piece of wood, eventually he would cut t so much that he would be able to cut it no longer; it would be too small. -
Antoine Lavoisier
Lavoisier is credited with being the "father of modern chemistry." He named both oxygen and hydrogen and predicted silicon. He also did an experiment leading up to the discovery of The Law of Conservation of Mass. -
Joseph Louis Proust
In 1799 Proust was studying sugar composition in Spain which led him to the Law of Constant Composition (later merged into the Law of Definite Proportions) stating no matter how a compound is produced or how much there is of it the reactants would always combine in the same way. Also produced the Plum Pudding model for atoms. -
John Dalton
In 1803 John Dalton finally finished his research and published his theory on atoms which stated that:
- All matter is comprised of small particles called atoms
- all atoms of a given element are alike
- compounds are formed when different atoms combine in fixed proportions
- a chemical reaction involves the rearrangement of atoms. -
Michael Faraday
He was mostly a scholar in electricity but when experimenting with diffusion (using chlorine), he studied the formed compounds. He eventually coined this with the term electrolysis. -
Marie and Pierre Curie
They studied radioactivity and eventually came upon two new chemicals; radium and polonium. Their research also lead to research in using radioactivity to treat illnesses such as cancer. -
Henri Becquerel
Henri is known for his discovery of radioactivity, for which he received the Nobel Prize for Physics jointly with Marie Curie (1897-1934) and Pierre Curie (1859-1906) in 1903 and the contributions he made to that field. -
JJ Thomson
created a tube with a positively charged anode side and a negatively charged cathode side which made sort of a beam then he placed a magnet in the middle and the beam bended toward the positive end of the magnet meaning the particles in the beam were negatively charged thus electrons. -
Max Planck
Planck discovered that electromagnetic energy is released in quantized specific amounts. In the formula to find the amount of energy that is released when electrons jump energy levels, h is plancks constant -
Ernest Rutherford
Gold Foil Experiment - He shot alpha particles at gold foil, most of them went right through the foil but some were reflected meaning there was a small, dense, positive charged area he called it a nucleus of an atom. -
Rpbert Millikan
Using the oil drop experiement he discovered that the overall charge of an atom is neutral and that the mass of an electron is very small -
Albert Einstein
used the idea of quanta (energy given off as light when an electron moves from a lower energy level to a higher one) to figure out the photoelectric effect in more detail. Which helped scientists learn where the electron clouds might be. -
Niels Bohr
Niels Bohr expanded upon his teacher Ernst Rutherford’s idea in 1913 Bohr stated that electrons stay in “clouds” and the farther away you get from the nucleus the more electrons these clouds can hold and the outer ones are what distinguishes the atoms chemical properties and when electrons jump form an outer orbit to an inner one light is emitted. -
James Chadwick
In 1932 James Chadwick discovered a new subatomic particle that he named the neutron. They have no charge and their function is to stabilize the nucleus of an atom by allowing protons to be close to one another. He discovered them by observing when Beryllium was hit with alpha particles it emitted a strange light and the substance that was emitting the light had no charge.
