20.4 The Group 6A Elements
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Transcript of 20.4 The Group 6A Elements
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20.4 The Group 6A Elements
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Oxygen Sulfur Selenium Tellurium Polonium
Group 6A Elements
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None of the Group 6A elements behave as typical metals
Most common behavior is to achieve a noble gas configuration by adding 2 electrons
This turns it into a 2- anion in ionic compounds with metal
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• Group 6A elements form covalent bonds with non metals
• Combine with hydrogen to form covalent hydrides with the general formula of H2X
• Those elements in Group 6A that have valence d orbitals(all but oxygen) form molecules commonly surrounded by more than 8 electrons
• Examples: SF4,SF6,TeI4, and SeBr4
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Selenium has an inverse relationship between cancer incidents and the amount of selenium in the soil
Seems that the intake of selenium intake protects against cancer
Selenium decency is also associated with congestive heart failure
Selenium
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20.5 The Chemistry Of Oxygen
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Most abundant element near and in the earth’s crust
Most common form 02 constitutes 21% of the atmosphere
The other form of elemental oxygen is 03 ozone
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Bond angle is 117 degrees(slightly less than 120 because of the lone pair)
Ozone is created by passing electric discharges through pure 02, which produce oxygen atoms. They then react with each other to form ozone
Ozone
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Ozone is a much stronger oxidizing agent then oxygen
Because of this oxidizing ability it can replace Chlorine in water purification
Chlorine residue, like chloroform, can cause cancer
The only problem with the use of ozone is that it is all used up and can’t protect against recontamination
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20.6 The Chemistry of Sulfur
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Sulfur found in large deposits of free elements and ores
About 60% of sulfur produced in the US is produced in elemental deposits in Texas and Louisiana
The Frasch Process is used to recover the sulfur: Pumping superheated water into the deposits to melt the sulfur. Then the sulfur is forced to the surface by air pressure.
Remaining 40% are by-products from purification of fossil fuels
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Unlike oxygen, Sulfur exists in S2 only as a gas at high temperature
Sulfur atoms form stronger sigma bonds then they do pi bonds
This means S2 is less stable than molecules like S6 and S8
The most stable sulfur is rhombic sulfur, which contains stacked S8 rings
When it cools it forms monoclinic sulfur, it also has stacked S8 rings, but stacked differently
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Sulfur monoxide(SO) can be produced when sulfur dioxide is subjected to electrical discharges
Sulfur burns in air to create Sulfur dioxide (SO2), colorless and has a pungent odor
SO2 is an effective antibacterial agent and is used in storing fruit
Sulfur oxides
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• Sulfur dioxide dissolves in water to create sulfurous acid(H2SO3)
• Sulfur trioxide dissolves in water to form sulfuric acid(H2SO4)
• Sulfuric acid is a powerful dehydrating agent as well as a strong oxidizing agent
Oxyacids of Sulfur
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The End