In what year was carbon (mineral) discovered and by whom?
438769
Carbon has been known since ancient times.  Diamond and graphite both occur readily in nature.
968818
Shanna and Geo06 have got this just about right.  The only thing I can add is that radiocarbon dating can not be used for more than about 70,000 years ago, and is more accurate for living things that died within the last 8,000 years.\n\nMost geologists measure rock ages in millions, or even billions, of years, so the age of the earth and the age of almost all igneous rocks is well beyond the range of carbon dating.  On top of that, igneous rocks contain very little if any carbon,  so carbon dating is not applicable here.  \n\nSo the only thing carbon 14 can be used for is to determine the time that an exchange of carbon with the atmosphere stopped, ie, the death of a living thing - the third item on your list of choices for your homework.\n\nThe half life of C-14, the radioactive isotope of carbon, is about 5730 years.  Therefore, if you know the ratio between C-14 and C-12 in the atmosphere when the organism died, and you know the ratio now, the difference in the ratio can be calculated backwards, using the half life, to estimate when the organism died. \n\nAtmospheric C-14 has not been in a constant ratio with C-12, as previously thought, so there are some serious problems with the accuracy of C-14 dating.  The problem is that the natural ratio of the carbon isotopes in the atmosphere (carbon dioxide) varies because cosmic ray bombardment of the outer atmosphere produces C-14 but not C-12.  The ratio can be predicted accurately using the ratios in old trees, where the tree rings can be used to accurately determine the age of each ring with its annual ratio, with a maximum of about 8,000 years -that's how old the oldest trees are which can establish a reference ratio.\n\nDating of artifacts is a best guess, the best method is to measure the amount of lichens growing on them, or the age of carbon in ashes found in the same spot.
796792
Thallium (Greek θαλλός, thallos, meaning "a green shoot or twig") was discovered by Sir William Crookes in 1861 in England while he was making spectroscopic determinations for tellurium on residues from a sulfuric acid plant. The name comes from Thallium's bright green spectral emission lines. In 1862 Crookes and Claude-Auguste Lamy isolated the metal independently of each other.
27404
It is believed that Albertus Magnus obtained the element in 1250 A.D. who obtained it by heating soap together with orpiment (arsenic trisulphide, As2S3). But actually Arsenic has been known since ancient times. It is so old, nobody knows who first discovered it or when. Arsenic compounds were mined by the early Chinese, Greek and Egyptian civilizations. No doubt they discovered its toxic properties early on. I don't know if anybody could find a name from the ancient history.
829227
Not sure you can get an exact ranking, because three were researched simultaneously:\n\nHelium was discovered on Earth in 1895 by Scottish chemist Sir William Ramsay, though some credit the discovery of helium (in the sun's spectrum) to Janssen and Lockyear in 1868. Ramsay discovered most of the remaining noble gases--argon in 1894 (with Lord Rayleigh) and krypton, neon, and xenon in 1898 (with Morris M. Travers). Radon was discovered in 1898 by Fredrich Ernst Dorn.
588452
Moissan was the first to *isolate* fluorine, no small feat - but the first person to identify it as a chemically-unique element (though in combination) was Scheele in 1771.
623434
It was discovered in 1817.  It was found associated with Tellurium.  During this time it was found in minerals such as crooksite and clausthalite.
93
Some evidence of photosynthesis was found on rocks in Greenland dating from 3.7 billion years ago. Danish researchers reached that conclusion analyzing the relative abundance of uranium and thorium in some rocks, and the high abundance of uranium in those suggests that there was oxygen present. Their conclusion was that microorganisms like present day cyanobacteria were converting sunlight to chemical energy through oxygen-producing photosynthesis.
417185
Carbon (C), Hydrogen (H), and Oxygen (O)
858037
carbon. because it can bond with more elements than any other, including itself.\n\nhence life is made out of it.\n\nit is extremely hard (diamond) and can be extremely soft (graphite). \n\nit doesnt have a melting point.
175106
There is carbon in EVERY organic material on earth ie...plants and animals.  When dead lifeforms decompose the result is carbon.
776734
It's called radio-carbon dating.\nhttp://en.wikipedia.org/wiki/Radio-carbon_dating
149295
carbon, hydrogen and oxygen.
912145
CO2 - the carbon atoms possibly are derived from hydrocarbons in food, and the oxygen atoms are, of course, from the atmosphere.
887230
During what perios of time ( like the century) did the most elements get discovered?
1027730
Oxygen was first discovered by Michał Sędziwój, a Polish alchemist and philosopher in the late 16th century. Sędziwój assumed the existence of oxygen by warming nitre (saltpeter). He thought of the gas given off as "the elixir of life".\nOxygen was again discovered by the Swedish pharmacist Carl Wilhelm Scheele sometime before 1773, but the discovery was not published until after the independent discovery by Joseph Priestley on August 1, 1774, who called the gas dephlogisticated air (see phlogiston theory). Priestley published his discoveries in 1775 and Scheele in 1777; consequently Priestley is usually given the credit. It was named by Antoine Laurent Lavoisier after Priestley's publication in 1775.
348304
Paleoanthropology.  Carbon dating and stuff like that.