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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 -
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 -
Dalton's Atomic Theory
All matter is composed of atoms, atoms cannot be made nor destroyed, all atoms of the same elements are identical, and different elements have different types of atoms. -
John Dalton
One of Dalton's discovery, which he made in 1804, which showed that if two elements have more than one combination, then weight amounts of one of them belonging to unchanging amount of the second one are staying in relations of small integers. -
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. -
James Chadwick
Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons - elementary particles devoid of any electrical charge. In contrast with the helium nuclei which are charged, and therefore repelled by the considerable electrical forces present in the nuclei of heavy atoms, this new tool in atomic disintegration need not overcome any electric barrier and is capable of penetrating and splitting the nuclei of even the heaviest elements. -
J.J. Thompson
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
The first ctr 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 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. -
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. Instead, as a quantum mechanically-influenced model, we shouldn’t know exactly where they are, and hence describe their probable location around the nucleus only as an arbitrary ‘cloud’. -
Plum Pudding 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. -
Rutherford Model
Rutherford overturned Thomson's model in 1911 with his well-known gold foil experiment in which he demonstrated that the atom has a tiny, massive nucleus. Rutherford designed an experiment to use the alpha particles emitted by a radioactive element as probes to the unseen world of atomic structure -
Henry Mosely
In 1913, Moseley observed and measured the X-ray spectra of various chemical elements (mostly metals) that were found by the method of diffraction through crystals. This was a pioneering use of the method of X-ray spectroscopy in physics, using Bragg's diffraction law to determine the X-ray wavelengths. Moseley discovered a systematic mathematical relationship between the wavelengths of the X-rays produced and the atomic numbers of the metals that were used as the targets in X-ray tubes. -
Neils Bohr
In 1922, Bohr was awarded the Nobel Prize in physics "for his services in the investigation of the structure of atoms and of the radiation emanating from them. The award recognized his early leading work in the emerging field of quantum mechanics. -
Erwin Shrodinger
In January 1926, Schrödinger published in Annalen der Physik the paper "Quantisierung als Eigenwertproble" on wave mechanics and presented what is now known as the Schrödinger equation.
