20.4 The Group 6A Elements

Oxygen Sulfur Selenium Tellurium Polonium

Group 6A Elements

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

• 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

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

20.5 The Chemistry Of Oxygen

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

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

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

20.6 The Chemistry of Sulfur

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

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

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

• 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

The End