My OperaApplication of Group 7 Elements
Sunday, February 28, 2010 1:27:38 PM
The halogens are the five chemical elements that make up Group 17 on the periodic table: fluorine, chlorine, bromine, iodine, and astatine. The halogens are all chemically active. For that reason, none occur naturally in the form of elements. However—with the exception of astatine—they are very widespread and abundant in chemical compounds. The most widely known of these compounds is sodium chloride, or common table salt.[/B][/FONT]
Fluorine[/I][/COLOR]
- It is one of the last common elements to be isolated
- It is one of the most dangerous chemicals known. It attacks the skin and throat, causing serious burns and respiratory problems at very low concentrations.
- Because it is so reactive, fluorine itself has few uses. One exception is its role as an oxidizing (burning) agent in rocket fuels.
- The most familiar application of fluorine compounds is in toothpaste additives.
- The most important group of fluorine compounds used commercially were the chlorofluorocarbons (CFCs). The CFCs were developed and used as refrigerants, blowing agents for polyurethane foam, and propellants in spray cans.
Chlorine[/I][/COLOR]
- To obtain chlorine, an electrical current is passed through brine, a water solution of sodium chloride.
- It is toxic. It attacks the respiratory tract, causing coughing, congestion, and flu-like symptoms. In high doses, it can be fatal. For this reason, chlorine was used as a chemical weapon during World War I.
- It is now widely used as a disinfectant in municipal water systems, swimming pools, and sewage treatment plants. Many organic (carbon-containing) compounds of chlorine are used as pesticides, herbicides, and fungicides.
- It is also used in the bleaching of paper, pulp, and textiles. The largest single application of the element is in the preparation of a large variety of compounds, including organic chlorides that are the starting point in the manufacture of plastics and other kinds of polymers.
Bromine[/I][/COLOR]
- The vapors are irritating to the eyes and throat. The liquid is highly corrosive and can cause serious burns if spilled on the skin.
- Can be used as a disinfectant. In fact, some water treatment systems have converted from chlorination to bromination as a way of purifying water.
- Bromine is also used to make a number of organic products that function as pesticides. The most popular of these currently is methyl bromide.
- The compounds of bromine can be used in photographic films.Tiny crystals of silver bromide undergo a chemical change when exposed to light. This change is responsible for the image produced when photographic film is used to take a picture.
Iodine[/I][/COLOR]
- Iodine vapor is irritating to the eyes and respiratory system. The human body uses iodine to make thyroxine, an important hormone (chemical messenger) produced by the thyroid gland.
- Iodine is also used commercially in a variety of products including dyes, specialized soaps, lubricants, photographic film, medicines, and pharmaceuticals.
Astatine [/I][/COLOR]
- Itis radioactive and is one of the rarest of the chemical elements. It has no practical applications at this time.
