Historical Development Of Atomic Structure :: essays research papers

Historical Development of Atomic Structure Yazan Fahmawi Sept. 30, 1995 T3 IBS Chemistry Ms. Redman The idea behind the "atom" goes back to the Ancient Greek society, where scientists believed that all matter was made of smaller, more fundamental particles called elements. They called these particles atoms, meaning "not divisible." Then came the chemists and physicists of the 16th and 17th centuries who discovered various formulae of various salts and water, hence discovering the idea of a molecule. Then, in 1766 was born a man named John Dalton born in England. He is known as the father of atomic theory because he is the one who made it quantitative, meaning he discovered many masses of various elements and, in relation, discovered the different proportions which molecules are formed in (i.e. for every water molecule, one atom of oxygen and two molecules of hydrogen are needed). He also discovered the noble, or inert gases, and their failure to react with other substances. In 1869 a Russian chemist, best known for his development of the periodic law of the properties of the chemical elements (which states that elements show a regular pattern ("periodicity") when they are arranged according to their atomic masses), published his first attempt to classify the known elements. His name was Mendeleyev, and he was a renowned teacher. Because no good textbook in chemistry was available at the time, he wrote the two-volume Principles of Chemistry (1868-1870), which later became a classic. During the writing of this book, Mendeleyev tried to classify the elements according to their chemical properties. In 1871 he published an improved version of the periodic table, in which he left gaps for elements that were not yet known. His chart and theories gained acceptance by the scientific world when three elements he "predicted"—gallium, germanium, and scandium—were subsequently discovered In 1856 another important figure in atomic theory was born: Sir Joseph John Thomson. In 1906, after teaching at the University of Cambridge and Trinity University in England, he won the Nobel Prize in physics for his work on the conduction of electricity through gases. He discovered what an electron is using cathode rays. An electron is the smallest particle in an atom, whose mass is negligible compared to the rest of the atom, and whose charge is negative. Though scientists did not know it at the time, electrons were located in an electron cloud rotating around the nucleus, or center of the atom. Another prominent figure in nuclear physics is a man called Ernest Rutherford, born in 1871. He also was a professor at the University of Cambridge, the University of Manchester (both of which are in England), and at McGill College