Helium

Helium DISCOVERY: A French astronomer, Pierre-Jules-C?sar Janssen (1824-1907), first obtained certainty for the existence of atomic number 2 during the solar eclipse of 1868 in India when he detected a new yellow line (587.49 nm) in the solar spectrum very close to the yellow sodium D-line. It was non possible to produce this line in the laboratory. Sir Norman Lockyer (1836-1920), an face astronomer, recognised that no known element at that era gave this line and named the element helium for the solarize. For many years helium was regarded as an element that might exist on the sun although it was unknown on the Earth.

Spectroscopists at the time doubted the results concerning helium. However the claims initiated a search for the new element on planet earth. In 1895, Sir William Ramsay detect helium after treating cleveite, a uranium mineral, with mineral acids. Ramsey sent samples of the gas to Sir William Crookes and Sir Norman Lockyer who identified helium. It was discovered independ...If you want to get a full essay, order it on our website: Ordercustompaper.com

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