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460
Democritus
Democritus said that all things originate from tiny, invisible particles, which he called atoms. His ideas were ignored.
460 B.C -
Period: 460 to
Atomic Theory
Democritus said that all things originate from tiny, invisible particles, which he called atoms. His ideas were ignored.
460 B.C -
Antoine Lavoisier
Lavoisier- father of modern chemistry, also an eminent physiologist. He clarified the concept of an element as a simple substance that could not be broken down by any known substance that could not be broken down by any known method of chemical analysis, and he also devised a theory of the formation of chemical compunds from elements. -
Law of Conservation of Mass
The Law of Conservation of Mass states that in a chemical reaction, the mass of the products equals the mass of the reactants and that matter is neither created nor destroyed by Antoine Lavoisier -
John Dalton
Dalton's theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights. All matter is composed of atoms, atoms cannot be made nor destroyed, all atoms of the same elements are identical, different elements have different types of atoms, chemical reactions occur when atoms are rearranged, and compounds are formed from atoms of the constituent elements. -
Dalton's Atomic Theory
All matter is composed of atoms, atoms cannot be made nor destroyed, all atoms of the same elements are identical, different elements have different types of atoms, -
Dmitri Mendeleev
Mendeleev is best known for his work on the periodic table; arranging the 63 known elements into a Periodic Table based on atomic mass/ His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties. He predicted the existence and properties of new elements and pointed out accepted atomic weights that were wrong. -
J.J Thomson
J.J discovered the electron and proposed a model for the structure of the atom. He knew that electrons had a negative charge and thought matter must have a positive charge. He became a physicist by default. -
Cathode Ray Tube
First CRT was invented by Karl Ferdinand Braun. A cathode is a terminal or electrode at which electrons enter a system, such as an electrolytic cell or an electron tube. A cathode ray is a stream of electrons leaving the negative electrode, or cathode, in a discharge tube or emitted by a heated filament in certain electron tubes. A cathode ray tube is a specialized vacuum tube in which images are produced when an electron beam strikes a phophorescent surface. -
Plum Pudding Atomic Model
An atom model proposed by J.J Thomson, he stated that the atom was like plum pudding. That the atom was a solid and massive thing of positive charge dotted with negative charges. -
Gold Foil Experiment
Ernest Rutherford described that the atom has a central positive nucleus and is surrounded by negative orbiting electrons. His model suggested that most of the mass of the atom was contained in a small nucleus, and the rest of the atom was empty space. Experiment involved firing of radioactive particles through thin metal foils and using screens to detect them, screens were coated with zinc sulfide. -
Robert Millikan
Millikan determined unit charge of the electron with his oil drop experiment. This allowed calculation of the mass of electrons and positively charged atoms. He went on to demonstrate the photoelectron effect, providing valuable proof of Albert Einstein's equations. His experiments aided both Einstein and Bohr/ -
Rutherford Model
Rutherford described that the atom has a central positive nucleus and is surrounded by negative orbiting electrons. His model suggested that most of the mass of the atom was contained in a small nucleus, and the rest of the atom was empty space. -
Ernest Rutherford
Rutherford conducted the gold foil experiment which was conducted to find out the structure of an atom -
Bohr Planetary Model
Created by Niels Bohr. Bohr expanded upon Rutherford's theory by proposing that electrons travel only in certain successivley larger orbits. He suggested that the outer orbits could hold more electrons than the inner ones, and that these outer orbits could determine that atom's chemical properties. He also described the way atoms emit radiation by suggesting that when an electron jumps from an outer orbit to an inner one, that it emits light. -
Niels Bohr
Bohr showed in a structure that the nucleus lies in the center of his model and is made up of a certain number of protons and neutrons. Each outer layer is made up of a certain number of electrons. -
Henry Moseley
Moseley determined the number of positive charges in the nucleus. -
Quantum Mechanical Model
The Quantum model is based on quantum mechanics (math) . Quantum numbers are quantum solutions to quantum equations and are used to find the probable position and location of an electron in an atom. The number of orbitals in a sub-level depends on the type of sub-level. To distinguish between the two electrons in an orbital, the electron-spin quantum number is used. there's two possible electron-spin quantum numbers 1/2 and negatie 1/2. 3 orbits. -
Erwin Schrodinger
Schrodinger stated that rather than electrons being distributed within an elctron configuration of shells and energy levels, they were arranged in orbits which were systematically distributed within elctron clouds. He defined the orbit as the region of space that surrounds a nucleus in which two elctrons may randomly move. -
James Chadwick
James Chadwick proved the existence of neutrons, resulting in the solution of the jig-saw puzzle for the weight of atoms. His discovery formed the base for the investigation of the tougher questions of nuclear physics: the nature of the nucleus and its forces. -
Electron Cloud Model
The electron cloud model is an atom model where electrons are no longer depicted as particles moving around the nucleus in a fixed orbit. Instead, as a quantum mechanically-influenced model. Discovered by Bohr, Rutherford, and Heisenburg
