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Elements are cooooool
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An English Scientist.
He was the first to define an element.
Today an element is defined to be "A substance composed of atoms with the same atomic number." -
John Dalton obtained symbols for elements and molecules. These symbols reflected his conclusions about the elements present.
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He conducted experiments by burning red mercury(II) oxide. The conclusion he go for this experiments was that during a chemical reaction, the mass of the reactants is equal to the mass of the product.
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He proposed that all elements were composed of atoms that were characteristic of that element. Chemical reactions involved the rearrangement of these atoms The root of all matter were very small particles called atoms which could not be divided or destroyed.
He developed the particle model of the atom. -
He was an analytical Chemist from Sweden.
He identified many chemical elements and hundreds of compounds.
He obtained the idea of using letters as symbols to stand for names of elements. -
He discovered the electron in 1897.
He developed an a atomic model that can be thought of as a “Plum Pudding.” -
He proposed, an atom is a dense, solid object that carries a positive charge but has negatively charged electrons distributed throughout.
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He conducted an experiment to test Thomson’s atomic ‘Plum pudding model.’
His experiment showed that Thomson’s model could not explain observations made by Rutherford’s alpha particle experiment -
Rutherford’s experiment consisted of firing alpha particles (Helium Atoms) at a sheet of gold foil.
He found, although most passed straight through, a few bounced back. These deflected particles had hit something solid. Which we now know is the nucleus -
He overcame the problems faced with Rutherford’s model.
He placed electrons in certain well defined orbits of fixed energy called electron shells. Bohr's model explained spectral emission from elements being observed at the time
