-
460
Democritus
Democritus was an ancient greek philosopher who formulated what s thought to be the first atomic theory. He claimed that atoms are physically, but not geometrically, indivisible; between atoms lies empty space; atoms are indestructible; atoms are always in motion; there are an infinite number of atoms and kinds of atoms, which differ in shapes, and sizes. -
Antoine Lavoisier
Antoine Lavoisier was a french chemist who found that mass is conserved in a chemical reaction.His results led to one of the fundamental laws of chemical behavior: the law of conservation of matter, which states that matter is conserved in a chemical reaction. -
John Dalton
John Dalton was an English physicist, his theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights. Dalton's Atomic Theory is that All matter is composed of atoms, atoms cannot be made or destroyed, all atoms of the same element are identical, different elements have different types of atoms, chemical reactions occur when atoms are rearranged, compounds are formed from atoms of the constituent elements. -
Dmitri Mendeleev
Dmitri Mendeleev was a Russian chemist and inventor. He formulated the Periodic Law and created created his own version of the periodic table of elements. He was also able to predict that there were other types of atoms that were yet to be discovered based on the gaps between elements in the periodic table. -
J.J Thompson
J.J Thompson was a British Physicist who discovered the electron during a series of experiments designed to study the nature of an electric discharge in a high vacuum Cathode Ray Tube.He claimed that an atom is one ball of positive energy with electrons scattered inside of it. His model is called the `Plum-Pudding Model'. -
Ernest Rutherford
Ernest Rutherford was a Physicist who discovered that atoms have a nucleus. He dicovered it during an experiment which invloved firing radioactive particles through thin metal foils and detecting them using screens coated with zinc sulfide.Rutherford found that although the vast majority of particles passed straight through the foil approximately 1 in 8000 were deflected leading him to beleive that an atom has a nucleus. -
Henry Moseley
Hennry Moseley was a British Chemist who studied under Ernest Rutherford. He developed the application of X-ray spectra to study atomic structure and found a more accurate positioning of elements in the Periodic Table by closer determination of atomic numbers. -
Robert Millikan
Robert A. Millikan was an American experimental physicist who determined the charge on an electron using charged oil drop experiments.His study established that any particular droplet's electrical charge is a multiple of a definite, fundamental value — the electron's charge. -
Niels Bohr
Niels Bohr is a physicist known for his contributions to quantum theory. He proposed that electrons are arranged in concentric circular orbits around the nucleus. This model is patterned on the solar system and is known as the planetary model. -
Erwin Schrodinger
Erwin Schrodinger is an Asutralian physicist who took the Bohr atom model one step further. Schrödinger 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. -
James Chadwick
James Chadwick was a physicist who proved the existence of a nuetron using evidence collected by Irene Joliot-Curie, who discovered that when beryllium was bombarded with positively charged alpha particles a beam with a high penetrating power was created.He discoverd that this beam was not deflected by either electric or magnetic fields, meaning it contained neutral particles- neutrons. -
The Current Theory
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons . The electrons of an atom are bound to the nucleus by the electromagnetic force.
