-
470 BCE
Democritus
Was born in the 80th Olympiad even though other scholars believed he was born about 470 BC. He is believed to have been born in Abdera in Thrace. He is believed to have died in 370 BC
He introduced the idea of the atom as the basic building block of all matter and everything is made up of atoms, his experiment was breaking a seashell in half. He proposed the first evidence based atomic theory. -
John Dalton
Born in Eaglesfield,England September 6,1766 His atomic theory said that all matter was made of atoms,invisible and indestructible building blocks,all atoms of an element are identical,atoms of different elements have diff. weights and diff. chemical properties,atoms of diff. elements combine in simple whole numbers to form compounds,and atoms cannot be created or destroyed when a compound decomposes the atoms are recovered unchanged He discovered the atomic theory by experimenting with gases -
Niels Bohr
Born on October 7,1885 in Copenhagen,Denmark died November 18,1962 made a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain quantities.First to discover that electrons travel in separate orbits around the nucleus and the number of electrons in the outer orbit determines the properties of an element did Bohr’s experiment -
J.J Thomson
Born in England in 1856 and died in 1940. Thomson discovered the electron through the Crookes tube, he then proposed a model of the atom which he compared to plum pudding. He said that negative electrons were the raisins in the pudding and the dough contained the positive charge. Thomson's model did explain some of the electrical properties of the atom due to the electrons, but failed to recognize the positive charges in the atom as particles.He developed the atomic theory. -
Cathode Ray tube experiment
JJ Thomson did this experiment, he used a cathode ray tube, which is a vacuum-sealed tube with a cathode and anode on one end that creates a beam of electrons that travel towards the other end of the tube. -
Gold Foil Experiment
The Gold Foil experiment was when Ernest Rutherford shot a beam of alpha particles at a sheet of gold foil, a few of the particles were deflected. He came to a conclusion that a tiny, dense nucleus was causing the deflections. -
Robert Millikan
He was born in 1868 & died in 1953. His oil drop experiment helped to quantify the charge of an electron which helped us understand the structure of the atom & atomic theory. In 1909 he started a series of experiments to determine the electric charge carried by a single electron. He started by measuring the course of charged water droplets in an electric field, but the results were not precise enough to be convincing. He got more precise results in 1910 with his oil drop experiment. -
oil drop experiment
The oil drop experiment helped to quantify the charge of an electron which contributed to our understanding of the structure of the atom&atomic theory.Millikan started by measuring the course of charged waterdroplets in an electric field.The results said that the charge on the droplets is a multiple of the elementary electric charge,but the experiment was not precise enough to be convincing.He obtained more precise results in 1910 with his oil-drop experiment in which he replaced water with oil. -
James Chadwick
James was assigned the task of tracking down evidence of Rutherford's tightly bound "proton-electron pair" or neutron. Rutherford had discovered the atomic nucleus in 1911. He also wrote the final draft of the MAUD Report, which inspired the U.S. government to begin serious atomic bomb research efforts. It was discovered that Beryllium, when bombarded by alpha particles, emitted a very energetic stream of radiation. Chadwick proposed that this was Rutherford's neutron. -
Ernest Rutherford
Born in New Zealand in 1871 & died in 1937. He was the first to discover that atoms have a small charged nucleus surrounded by largely empty space & are being circled by tiny electrons which then became known as the Rutherford model of the atom. He came to know and understand the gold-foil experiment which led him to then discover and create the Rutherford model of the atom. He studied under JJ Thomson and he got a Nobel Prize for chem in 1908, he was known as the father of nuclear physics. -
Erwin Schrodinger
Erwin Schrodinger was born in Austria in 1887 and died in Austria in 1961. Erwin was responsible for the wave equation for electron movement and he proposed it in 1926. He was awarded the Nobel Prize in 1933 for physics. He 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. He achieved fame for quantum mechanics.
