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Caesium (IUPAC spelling; [9] also spelled cesium in American English) is a chemical element; it has symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C (83.3 °F; 301.6 K), which makes it one of only five elemental metals that are liquid at or near room temperature.
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]
Johan Gadolin discovered the earth in gadolinite in 1794. He did not name his discovery, but Andreas Ekeberg did so when he confirmed it in 1797. [1] Mosander showed later that its ore, yttria, contained more elements. [99] [100] In 1808, Davy showed that yttria is a metallic oxide, although he could not isolate the metal.
For example, germanium was called eka-silicon until its discovery in 1886, and rhenium was called dvi-manganese before its discovery in 1926. The eka-prefix was used by other theorists, and not only in Mendeleev's own predictions. Before the discovery, francium was referred to as eka-caesium, and astatine as eka-iodine.
An image from John Dalton's A New System of Chemical Philosophy, the first modern explanation of atomic theory.. This timeline of chemistry lists important works, discoveries, ideas, inventions, and experiments that significantly changed humanity's understanding of the modern science known as chemistry, defined as the scientific study of the composition of matter and of its interactions.
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.
The planet is about the size of Venus, so slightly smaller than Earth, and may be temperate enough to support life, the researchers said. Dubbed Gliese 12 b, the planet takes 12.8 days to orbit a ...
[39] [40] Rubidium was the second element, shortly after caesium, to be discovered by spectroscopy, just one year after the invention of the spectroscope by Bunsen and Kirchhoff. [ 41 ] The two scientists used the rubidium chloride to estimate that the atomic weight of the new element was 85.36 (the currently accepted value is 85.47). [ 39 ]