Research With Sir J.J. Thomson

In the end of 1909, Aston accepted Tomson invitation to work as his assistant, at the Cavendish laboratory, in Cambridge on the studies of positive rays. It was also during this period that he obtained definite evidence for the existence of two isotopes of the inert gas neon. Thomson had alredy been working on positive rays since 1906, and he was ready to used crossed electric magnetic deflections to do the first primitive mass analysis. When aston join Thomson in the research he helped design some of the high vacuum equipment needed for this research. Together, they unknowingly witnessed the first evidence of isotopes in stable elements. As the particles sped through the electric and magnetic deflections, they created parabolas, showing the path taken through the feilds. From these parabolas, they determined atomic mass for many elements.When World War I broke out, Aston and Thomson stop their research.

Isotopes and Atomic Weight

The experiment of Isotopes and atomic weights had been carry out in the 20th centry. It indicated that radioactive substances that were chemically inseparable might be different from each other only in the structure of their nuclei. In 1912, a physicist Sir J.J. Thomson demonstrated the existence of stable isotopes by passing neo throuh a discharge tube and deflecting the eo io by means of magnetic and electric field; This show hat the stable eleent neon exists in more than one form. Research on isotopes was continue by many scientists, notably the british physicist Francis william Aston; their wok in detecting and studyig isotopes was accelerate by the developement of the mass spectrometer. It is now know that most element in the nature state consist of a mixture of two or more isotopes. mong the exception are beryllium, aluminum, phosphorus, and sodium. The chemical atomic weight of an element is the weights or mass numbers of the isotopes. For exale, chlorine atomic weight s 35.457, is compose of chlorine-35 and chlorine-37, the former occuring with an abundance of 76% and the latter of 24%. All the isotopes of elements with atomic numbes higher than 83 are radiactive, n a fewof the lighter isotopes, sich as potassium-40 are radioactve. About 280 naturally occuring stable isotopes, not radioactive are know.