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300
Democritus
In the atoms are indestructible units which means that they are stable and they do not break apart. The atoms change form and move around to combine different forms of a molecule. He also made up a term named, Atomos. Atomos are matter can be cut until it can not be cut anymore. -
Period: 300 to
Atomic Theory
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Antonie Lavoisier
He introduced the metric system, Introduced the identification of hydrogen and oxygen -
Law of Conservation of Mass
It was established in 1789 by a french scientist by the name of Antoine Lavioser. It states that mass is neither created nor destroyed. -
Daltons Atomic Theory
He proposed the Law of Multiple Proportions. This law led directly to the proposal of the Atomic Theory in 1803. -
John Dalton
He developed the concept of the mole and proposed a system of symbols to represent atoms of different elements. He recoginized the existence of atoms of elements and that compounds formed from the union of these atoms. He therefore assumed that simplest ratios would be used in nature and came up with a formula for water. He then assigned a relative atomic weight of one to hydrogen and developeda relative atomic weight scale. -
Dmitir Mendeleev
Credited as being the creator of the first periodic table of elements. -
Cathode Ray Tube
Its a vacuum tube containing one or more electron guns (a source of electrons or electron emitter) and a fluorescent screen used to view images. -
JJ Thomson
Credited for finding the first element for Isotopes of a stable element in 1913. -
Plum Pudding Atomic Model
An atomic model that was proposed by J.J thompson, the Physist who discovered the electroon. -
Robert Millikan
As a scientist, Millikan made numerous momentous discoveries, chiefly in the fields of electricity, optics, and molecular physics. His earliest major success was the accurate determination of the charge carried by an electron, using the elegant "falling-drop method"; he also proved that this quantity was a constant for all electrons (1910), thus demonstrating the atomic structure of electricity. -
Rutherford Model
Is a model of the atom devised by Ernest Rutherford. -
Henry Moseley
Moseley's law advanced atomic physics by providing the first experimental evidence in favour of Niels Bohr's theory, aside from the hydrogen atom spectrum which the Bohr theory was designed to reproduce -
Niels Bhor
Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete, and that they revolve in discrete, stable orbits around the atomic nucleus, akin to planets around the sun, except that they can jump from one energy level (or orbit) to another. -
Bohr Planetary
The Bohr Model is probably familar as the "planetary model" of the atom illustrated in the adjacent figure that, for example, is used as a symbol for atomic energy (a bit of a misnomer, since the energy in "atomic energy" is actually the energy of the nucleus, rather than the entire atom). In the Bohr Model the neutrons and protons (symbolized by red and blue balls in the adjacent image) occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbit -
Gold Foil Experiment
Made an experiment to prove the structure of the atom. -
Erwin Schrodinger
He developed a number of fundamentals resluts in the field of the quantum theory, which formed the basis for mechanics. -
Quantum Mechanical Model
The quantum mechanical model is based on quantum theory, which says matter also has properties associated with waves. According to quantum theory, it’s impossible to know the exact position and momentum of an electron at the same time. This is known as the Uncertainty Principle. -
James Chadwick
was an English physicist who was awarded the 1935 Nobel Prize in physics for his discovery of the neutron in 1932. -
Electron Cloud Model
The electron cloud model is an atom model wherein electrons are no longer depicted as particles moving around the nucleus in a fixed orbit -
Ernest Rutherford
In early work he discovered the concept of radioactive half-life, proved that radioactivity involved the transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation.
