Science, Technology

John Dalton
JJ Thompson

Who was john Dalton?

John Dalton was born in 1766. He was born into a modest family in Cumberland, England. He earned a living for most of his life as a school teacher and a public lecturer. After teaching 10 years at a boarding school in Kendal, he moved on to a teaching position in the city of Manchester. There he joined the Manchester Literary and Philosophical Society, which provided him with a stimulating intellectual environment and laboratory facilities. The first paper he delivered before the society was on color blindness, and died in 1844.

Dalton joined the Manchester Literary and Philosophical Society and immediately published his first book on Meteorological Observations and Essays.

In this way, Dalton was able to start working out a table of atomic weights based on the lightest element, hydrogen, having a value of 1. He used his ideas about the make up of gasses this way, "we may form an idea of this by supposing a vessel filled with small spherical leaden bullets among which a quantity of fine sand is poured. The balls are to the sand as the particles of bodies are with respect to the caloric; with this difference only, that the balls are supposed to touch each other, whereas the particles of bodies are not in contact, being retained at a small distance from each other by the caloric." (Dalton)

Dalton's thoughts on his research allowed him to develop his theory were All matter was made up of hard round particles, which he called 'atoms', and that each type of atom, or element, such as hydrogen, oxygen, nitrogen, etc., differed from the next only by its weight.

The atomic theory had been born....
But his next idea was one of equal genius, how to represent this idea symbolically so that tiny, invisible particles could be 'seen' and their combining properties studied.

The solution was that Dalton thought, was to draw circles, each circle representing one of his tiny atomic spheres. Each element could be notable by the contents of the circle.

Who Was Joseph John Thompson?

Joseph John Thompson better known as JJ Thompson, was born on December 18, 1856 near Manchester, England. His father died when "JJ Thompson" was only sixteen. JJ attended Owens College in Manchester, where his professor of mathematics encouraged him to apply for a scholarship at Trinity College, one of the most important of the colleges at Cambridge University. JJ won the scholarship, and in 1880 finished second in his class (behind Joseph Larmor) in the grueling graduation test in mathematics. Trinity gave him a fellowship and he stayed on there, trying to craft mathematical models that would reveal the nature of atoms and electromagnetic forces. He also died in 1940.

In 1897 Joseph John Thompson discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube—an area being investigated by numerous scientists at the time. Thomson interpreted the deflection of the rays by electrically charged plates and magnets as evidence of "bodies much smaller than atoms" that he calculated as having a very large value for the charge to mass ratio. Later he estimated the value of the charge itself. In 1904 he suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces. His efforts to estimate the number of electrons in an atom from measurements of the scattering of light, X, beta, and gamma rays initiated the research trajectory along which his student Ernest Rutherford moved. Thomson's last important experimental program focused on determining the nature of positively charged particles. Here his techniques led to the development of the mass spectroscope, an instrument perfected by his assistant, Francis Aston, for which Aston received the Nobel Prize in 1922.

Who Was Ernest Rutherford?

Ernest Rutherford was born on August 30, 1871, in Nelson, New Zealand, the fourth child and second son in a family of seven sons and five daughters. His father James Rutherford, a Scottish wheelwright, emigrated to New Zealand with Ernest's grandfather and the whole family in 1842. His mother, Née Martha Thompson, was an English schoolteacher.

Ernest received his early education in Government schools and at the age of 16 went to Nelson Collegiate School. In 1889 he was awarded a University scholarship and he proceeded to the University of New Zealand, Wellington, where he entered Canterbury College. He graduated M.A. in 1893 with a double first in Mathematics and Physical Science and he continued with research work at the College for a short time, receiving a degree the following year. That same year, 1894, he was awarded an 1851 Exhibition Science Scholarship, enabling him to go to Trinity College, Cambridge, as a research student at the Cavendish Laboratory under J.J. Thomson. In 1897 he was awarded the B.A. Research Degree and the Coutts-Trotter Studentship of Trinity College. An opportunity came when the Macdonald Chair of Physics at McGill University, Montreal, became vacant, and in 1898 he left for Canada to take up the post.

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