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Chalcogens Group (6)
Transcript of Chalcogens Group (6)
Oxygen was discovered by a pharmicist named Carl Wilhelm Scheele. Scheele made oxygen by heating mercuric oxide and many different nitrates by around 1722. Seeing that it was combustible, he named it "fire air" and had his document about it published around 1777. During 1774, however, a British clergyman named Joseph Priestley, focused sunlight on mercuric oxide and didn't find it different than regular air. Another man named Antoine Laurent Lavoisier, also said he had discovered something like this and got an explanation of Priestley's experiment by Priestley about his results, as well as Scheele who was going to send a letter to Lavoisier about his however never got one since Scheele died later on. and uses... Sulfur Atomic Structure Now lets start with Sulfur. Physical Properties Sulfur is a tasteless, oderless, and light yellow solid. It can also combine with all other elements other than gases, gold, and platinum. Some other physical properties:
-Atomic Mass: 32.066
-Melting point: 388.36 K (115.21°C or 239.38°F)
-Boiling point: 717.75 K (444.60°C or 832.28°F)
-Magnetivity: None -Atomic mass of oxygen: 15.9994
-Melting point: -218.4 °C (54.750008 K, -361.12 °F)
-Boiling point: -183.0 °C (90.15 K, -297.4 °F) Chemical Properties Sulfur is a non-metal which is characterized by a yellow color as a solid however as a liquid it is known to be quite red (picture to the right) and if it is burned and becomes a liquid it emits a blue flame. Obtained...how? What is it used for? Oh and who discovered it? Sulfur is usually obtained in meteorites and most commonly found in volcanoes and hot springs. It is also recovered from wells deep in the Gulf of the U.S.
Uses for sulfur are for black gunpowder, and the vulcanization of rubber and fungicide. It is also used to make fertilizer and it is largely contributed towards sulfuric acid, the most widely used chemical, as well as different papers and it is essential for us to live since we have it making up lots of our fats, body fluids, and skeletal minerals.
Sulfur was known in ancient times, as it is reffered to in Genisis in the Bible. By 1044 AD, the Chinese used sulfur in their gun powder and in 1777 Antoine Lavoisier determined that sulfur was an element and not a compound. So all in all, nobody is actually sure who discovered sulfur. Tellurium Atomic Structure Physical Properties Tellurium is a silvery white metal-looking non-metal that is usually obtained as a dark grey powder.
-Atomic Mass: 127.6
-Melting point: 722.8K 449.65°C 841.37°F
-Boiling point: 1261K 988°C 1810°F Chemical Properties Some of the things that tellurium cannot react with are things like oxidizers and chlorine. Tellurium is also unaffected by water and hydrochloric acid, however it dissolves in nitric acid. Also, when burned in air tellurium has a greenish-blue flame and forms tellurium dioxide as a result. How is tellurium obtained? Who discovered it? Tellurium was founded by a man named Franz Joseph Müller von Reichenstein, a Romanian mining official, in 1782. Reichenstein was the cheif of mining, smelting, etc. during the time and he also had a keen interest in chemistry. One day he had extracted an ore from gold which he had thought was antimony, however he was mistaken and it was an unknown element. Later on in 1798 a German scientist named Martin Heinrich Klaproth, mentioned that it was in paper and named this new element tellurium, but Reichenstein was still given full credit.
Tellurium is found in nature, but is most often found in the ores sylvanite (AgAuTe4), calaverite (AuTe2) and krennerite (AuTe2). Today, most tellurium is obtained from the mining and refining of copper. What is tellurium used for? Tellurium has many uses these days like coloring glass for example in ceramics, as well as being used as an alloying agent. Small amounts of tellurium are added to copper and stainless steel to make them easier to mill and machine. Tellurium is also a semi conductor. It becomes a great infared sensitive conductor when alloyed with cadmium and mercury, for example. Selenium Atomic Structure Physical Properties Selenium is a dark gray or dark red type of crystal of non-metal. It burns in contact with air, but is unaffected by water.
Atomic Mass: 78.96
Melting point: 494K 221°C 430°F
Boiling point: 958K 685°C 1265°F Chemical Properties
Selenium is a fairly reactive element which
combines easily with hydrogen, fluorine, chlorine, and bromine, as well as many metals. Selenium's resistance to the flow of electricity is greatly affected by the amount of light shining on it. The brighter the light, the better selenium conducts electricity. Here, selenium is being burned. How is selenium obtained? Who discovered it? Selenium was discovered by the Swedish scientist, Jöns Jacob Berzelius, in 1817. He discovered this element after finding an impurity in the creation of sulfuric acid. At first, he thought it was tellurium, but soon realized it was an unknown element. Selenium is mostly obtained from the refining of copper. What is selenium used for? Selenium is, beleive it or not, very good for you. It is an anitoxidant and can help stop/prevent cancer and heart disease. Selenium is located in every tissue of your body and it helps to activate glutathione. This is an enzyme which protects cells from oxidative stress. Selenium is also used to give red color to glass, and it is also used in photography.