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Robert Wilhelm Eberhard Bunsen (German:; 30 March 1811 [a] – 16 August 1899) was a German chemist.He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with the physicist Gustav Kirchhoff. [11]
[note 1] [74] [75] [76] Caesium was the first element to be discovered with a spectroscope, which had been invented by Bunsen and Kirchhoff only a year previously. [ 17 ] To obtain a pure sample of caesium, 44,000 litres (9,700 imp gal; 12,000 US gal) of mineral water had to be evaporated to yield 240 kilograms (530 lb) of concentrated salt ...
Perey discovered it as a decay product of 227 Ac. [177] Francium was the last element to be discovered in nature, rather than synthesized in the lab, although four of the "synthetic" elements that were discovered later (plutonium, neptunium, astatine, and promethium) were eventually found in trace amounts in nature as well. [178]
Gustav Robert Kirchhoff (German: [ˈgʊs.taf ˈkɪʁçhɔf]; 12 March 1824 – 17 October 1887) was a German physicist, mathematican and chemist who contributed to the fundamental understanding of electrical circuits, spectroscopy and the emission of black-body radiation by heated objects.
With the new data, he published "Age of Meteorites and the Earth" in 1956, the first paper explaining the "true" age of the solar system's accretion as 4.550Gy ± 70My; [9] [10] [1] [11] a figure that has remained largely unchallenged since. Before his paper, it was largely believed the earth was around 3.3 billion years old.
5th century BC: The earliest documented mention of a spherical Earth comes from the Greeks in the 5th century BC. [31] It is known that the Indians modeled the Earth as spherical by 300 BC [32] 460 BC: Empedocles describes thermal expansion. [33] Late 5th century BC: Antiphon discovers the method of exhaustion, foreshadowing the concept of a limit.
From ancient history to the modern day, the clitoris has been discredited, dismissed and deleted -- and women's pleasure has often been left out of the conversation entirely. Now, an underground art movement led by artist Sophia Wallace is emerging across the globe to challenge the lies, question the myths and rewrite the rules around sex and the female body.
To give provisional names to his predicted elements, Dmitri Mendeleev used the prefixes eka- / ˈ iː k ə-/, [note 1] dvi- or dwi-, and tri-, from the Sanskrit names of digits 1, 2, and 3, [3] depending upon whether the predicted element was one, two, or three places down from the known element of the same group in his table.