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Democritus
Democritus was an acient Greek philosopher who formulated the Atomic Theory of the Universe. He was the first to believe that everything on earth, is composed of atoms. Some of his theories include are, atroms are physically, but not geometrically, indivisible; that between atoms, there lies empty space; that atoms are indestructible; have always been, and always will be, in motion; that there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size -
John Dalton
John Dalton was an English chemist. n 1800, Dalton became a secretary of the Manchester Literary and Philosophical Society, and in the following year he orally presented an important series of papers, entitled "Experimental Essays" on the constitution of mixed gases; on the pressure of steam and other vapours at different temperatures, both in a vacuum and in air; on evaporation; and on the thermal expansion of gases. -
Joseph John Thomson
In 1897, Thomson disovered that cathode rays were composed of a previously unknown negatively uncharged particle. By doing this, he had made the discovery of the electron, which led to a whole new world on science. Also in 1913, he was credited with finding the first pieces of evidence for isotopes in a stable element. -
Ernest Rutherford
Ernest Rutherford was a British physicist who became known as the father of nuclear physics. Early in his work, he discovered the concept of radioactive half-life. This proved that radioactivity involved the transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation. -
Niels Bohr
Neils Bohr was a Danish physicist who made contributions to understanding the atomic structure, and the quantum theory. Bohr developed the Bohr model of an atom, which proposed that energy levels of electrons are discrete. It also includes that electrons stay in stable orbits around the atoms nucleus, but can jump energy levels. -
Modern Atomic theory
The modern atomic theory consists of a nucleus, which contains protons and nuetrons. On the shells of the atom, there are negatively charged electrons, that orbit the nucleus.
