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Robert Wilhelm Eberhard Bunsen (German: [ˈʁoːbɛʁt ˈbʊnzn̩]; 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]
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.
Note: René Haüy discovered that emeralds and beryls crystals are geometrically identical. He asked Vauquelin for a chemical analysis, and so Vauquelin found a new "earth" (beryllium oxide). Carl Wilhelm Scheele (1742 –1786), discovery of oxygen with Priestley; identification of molybdenum, tungsten, barium, hydrogen, and chlorine.
Perey discovered it as a decay product of 227 Ac. [183] 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. [184]
The goal of Earth Day 2014 was to dramatically personalize the massive challenges surrounding global climate change and weave that into both Earth Day 2014 and the five-year countdown to Earth Day 2020, the 50th anniversary. It was an opportunity to unite people worldwide into a common cause and call for action. [110]
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.
The first eon in Earth's history, the Hadean, begins with Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of Earth's crust and Earth itself.