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Information about the halogens group, including their historical discoveries, physical properties, and uses. Topics covered include the discovery of each halogen, their diatomic molecules, electron configuration, common ionic charges, important compounds, and reactions. The document also discusses the importance of halogens in various industries and everyday life, such as tooth decay prevention and swimming pool chemistry.
Typology: Schemes and Mind Maps
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R32 Elements Handbook
Elements HandbookHandbook
Fluorine | discovered in 1886 by Henri Moissan
Chlorine | discovered in 1774 by Carl Wilhelm Scheele
Bromine | discovered in 1826 by Antoine-Jérôme Balard
Iodine | discovered in 1811 by Bernard Courtois
Astatine | discovered in 1940 by Dale R. Corson, K. R. Mackenzie, & Emilio Segrè
There are vapors in the bromine and iodine tubes because bromine is volatile and iodine sublimes easily at room temperature.
Fluorite, CaF 2 , is the principal mineral of fluorine. The term fluorescent comes from this mineral, which glows in the presence of UV radiation.
85
Astatine (210)
(^28) (^1832) (^187)
53
Iodine 126.
(^28) (^1818) 7
35
Bromine 79.
(^28) (^187)
17
Chlorine 35.
(^28) 7
9
Fluorine 18.
27^ Br^2
Cl 2
2
Density 4.
3.
2 1 0
3
4
5
Density (g/cm
3 )
1.81 10 ^3
3.21 10 ^3
F Cl Br
Melting and Boiling Points
0
300
200
100
100
200
Temperature (
C)^114
184
59 (^35) 7 101 mp
(^188) bp
F Cl Br
220
Richard Megna/Fundamental Photographs
1987 Paul Silverman/Fundamental Photographs
Group 7A: Halogens R
2Na( s ) Cl 2 ( g ) 2NaCl( s ) H 411 kJ/mol
H 2 ( g ) Cl 2 ( g ) 2HCl( g ) H 92.3 kJ/mol
Chlorine reacts vigorously with sodium to form solid sodium chloride.
Electronegativity
0
Electronegativity
4.
2.5 (^) 2.
3.0 (^) 2.
F Cl Br At
First Ionization Energy
1681
(^1009 )
(^1256 )
600
0
1200
1800
Energy (kJ/mol)
F Cl Br At
Atomic radius (pm)
Ionic radius (pm)
F Cl Br I At
F –^ Cl –^ Br –^ I–
62 102 120 140 140
133 181 196 220
Hypochlorite Chlorite
1 1
Chlorate
1
Perchlorate
1
Richard Megna/ Fundamental Photographs
Group 7A: Halogens R
The most important function of blood is its ability to deliver oxygen from the lungs to cells throughout the body, and carry carbon dioxide from the cells to the lungs. Blood transfusions have been the traditional response to blood loss due to severe injuries or surgery. Blood transfusions have saved millions of lives. But it takes time to determine the recipient’s blood type and less common blood types may not be available. Also, blood can carry disease-causing bacteria and viruses.
Some artificial blood contains perfluorocarbons (PFCs). PFCs are organic compounds in which all the hydrogen has been replaced by fluorine. PFCs can dissolve and transport large quantities of oxygen. PFCs are mixed with emulsifiers and salts that mimic the composition of blood, minus the cells.
Large amounts of PFCs can be manufactured and their purity controlled. PFCs can deliver oxygen to areas where blood flow is restricted by narrowed arteries or tumors. In current trials, artificial blood is used to delay the need for blood transfusions during surgery. Because PFCs carry less oxygen than hemo- globin does, the patient must breathe oxygen-rich air.
Because blood is so complex, scientists may never find a sub- stitute to perform all its functions. Therefore, there is still a great need for donations of human blood. ■
The liquid in the beaker is a perfluorocarbon that is saturated with oxygen. The mouse survived by absorbing oxygen from the liquid in its lungs.
The thyroid gland produces hormones that help to control the body’s growth and the energy produced by cells. Trace amounts of iodine are needed to produce thyroid hormones. An adult needs about 150 mg of iodine daily.
Ocean fish are a good source of iodine. When people used to get most of their food from local sources, a person who lived far from the ocean often had an iodine deficiency.
To compensate for the lack of iodine, the thyroid gland might enlarge. A severe deficiency could cause mental retardation. Adding potassium iodide to table salt proved to be a simple solution to this public health problem.
In the United States, iodized salt was first sold in 1924. There is about 400 mg of iodine in a teaspoon of iodized salt.
The use of iodized salt has virtually eliminated the problem of iodine deficiency in the United States. ■
The purple dye prized by Roman emperors and other rulers contains bromine. The dye was extracted from the mollusk Murex brandaris, which lives in the Mediterranean Sea.
Group 7A: Halogens R
Gwen Rosenberg/Alliance Pharmaceutical Corp.
Carolina Biological Supply Company/Phototake