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Period: 470 BCE to
Contribution To the Atomic Theory
All of these scientists, experiments, and laws and theories contributed into developing the atomic theory even more. -
Period: 460 BCE to 370 BCE
Democritus
Democritus expanded the atomic theory of Leucippus. He supposed the atoms, which are originally similar, to be impenetrable and have a density proportionate to their volume. Basically this means, you can't further than an atom, the smallest element and there's a correlation between the density and volume of a substance. -
Law of Conservation of Mass
The law of conservation of mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants. -
Antoine Lavosier
He established the Law of Conservation of Mass, stating that mass is not created nor destroyed through conservation, but observed. According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants. -
Dalton's Atomic Theory
Dalton's Atomic Theory are all matter is made of atoms. Atoms are indivisible and indestructible. All atoms of a given element are identical in mass and properties. Compounds are formed by a combination of two or more different kinds of atoms. A chemical reaction is a rearrangement of atoms. -
Dmitri Mendeleev
Mendeleev is known for his work on the Periodic Law and creation of the first Periodic table. In 1869, he created the first Periodic Table. The Periodic Law states that when elements are arranged according to their atomic number, elements with similar properties will appear at regular intervals. -
J.J Thompson
In 1897 Thomson discovered the electron and then went on to propose a model for the structure of the atom. His work also led to the invention of the mass spectrograph. -
Plum Pudding Model
The 'plum pudding' model of the atom was proposed by JJ Thomson, who had also discovered the electron. It was put forth before the discovery of the nucleus. This model is wrong, however. It was disproved by Rutherford's Gold Foil Experiment. -
Ernest Rutherford
He suggested the nuclear structure of the atom. -
Rutherford's Gold Foil Experiment
By carefully measuring the fraction of the -particles deflected through large angles, Rutherford was able to estimate the size of the nucleus. According to his calculations, the radius of the nucleus is at least 10,000 times smaller than the radius of the atom. The vast majority of the volume of an atom is therefore empty space. -
Henry Mosley
Henry Moseley studied under Rutherford and brilliantly 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. -
Bohr Planetary Model
In 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. -
Robert A. Millikan
Robert Millikan measured the charge on an electron. By carefully studying individual droplets, Millikan was able to show that the charge on a drop was always an integral multiple of a small, but finite value. -
Erwin Schrödinger
Assuming that matter (e.g., electrons) could be regarded as both particles and waves, in 1926 Erwin Schrödinger formulated a wave equation that accurately calculated the energy levels of electrons in atoms. -
Quantum Mechanical Model
The quantum mechanical model of the atom uses complex shapes of orbitals (sometimes called electron clouds), volumes of space in which there is likely to be an electron. So, this model is based on probability rather than certainty. -
Electron Cloud Model
It is used to describe where electrons are when they go around the nucleus of an atom. -
James Chadwick
Chadwick is best known for his discovery of the neutron in 1932. Bombarding elements with neutrons can succeed in penetrating and splitting nuclei, generating an enormous amount of energy.
