1800-1875+(VC)

Sir William Crookes


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-He constructed the forerunner of the modern TV picture tube in the 1870's strictly to investigate the properties of cathode rays.Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. He was the sole pioneer of vacuum tubes in which he called them "Crookes tubes". He also discovered the element as we know today thallium from the Greek word thallos meaning a green shot. He identified the first sample of helium and also invented the Crookes radiometer.

__**Sir William Crooke's Bio**__ He was born in London on June 17, 1832. From 1850-1854 in the Royal College he embarked upon original work on the new compounds of selenium. When he left, he became the superintendent of the meteorological department at the Radcliffe Observatory in Oxford. He died on April 4th, 1919.

**John** Dalton


-Dalton's greatest achievement was the atomic theory. "It all began with the attempt to explaining why the constituents of a gaseous mixture remain homogeneously mixed instead of forming layers according to their density."

1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms.
 * Dalton's Atomic Theory (1808)**

__**John Dalton's Bio**__ John Dalton was born around September 6th, 1766 (there are no exact record that exists) into a Quaker family in Eaglesfield, England. He was the youngest of three surviving children of a Quaker handloom weaver. He attended school until age 11 and once he turned 12, he became a teacher and a public lecturer. The first paper he delivered before the society was on color blindness, which afflicted him and is sometimes still called "Daltonism." After teaching for over ten years at Kendal, a Quaker boarding school, he taught in the city of Manchester. He was an English chemist providing the beginnings of the development of a scientific atomic theory. Dalton also contributed to physics, mostly meteorology.