http://www.ck12.org Chapter 2. Matter
TABLE2.11:(continued)
Halogen Use
Bromine is used to purify water in swimming pools and
hot tubs. It reacts with bacteria and other germs and
renders them harmless.Iodine is added to alcohol and used as an antiseptic. It
reacts with germs on cuts and wounds. Small amounts
of iodine are also needed for good health. In the
U.S., iodine is added to table salt to prevent iodine
deficiencies. Does the salt you use contain iodine?Q:Can you relate some of these uses of halogens to the properties of these elements?
A:The ability of halogens to kill germs and bleach clothes relates to their highly reactive nature.
Summary
- Halogens are highly reactive nonmetal elements in group 17 of the periodic table.
- Halogens include solids, liquids, and gases at room temperature, and they vary in color.
- Halogens are among the most reactive of all elements. They have seven valence electrons, so they are very
“eager” to gain one electron to have a full outer energy level. - Halogens have a variety of important uses, such as preventing tooth decay and killing germs.
Vocabulary
- halogen: Nonmetal in group 17 of the periodic table that has seven valence electrons and is highly reactive.
Explore More
TheTable2.12 gives the melting and boiling points of halogens. Create a graph with the data, and then describe in
words the trends that you see in your graph.
TABLE2.12: Melting and Boiling Points of Halogens
Halogen Melting Point (°C) Boiling Point (°C)
Fluorine -220 -188
Chlorine -101 -35
Bromine -7 58
Iodine 114 184
Astatine 302 337Review
- What are halogens?
- Why are halogens very reactive?