2.55. Halogens http://www.ck12.org
Physical Properties of Halogens
The halogen group is quite diverse. It includes elements that occur in three different states of matter at room
temperature. Fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids. Halogens also
vary in color, as you can see in theFigure2.116. Fluorine and chlorine are green, bromine is red, and iodine and
astatine are nearly black. Like other nonmetals, halogens cannot conduct electricity or heat. Compared with most
other elements, halogens have relatively low melting and boiling points. You can watch a lab demonstration of the
melting and boiling points of halogens at this URL: http://www.youtube.com/watch?v=yP0U5rGWqdg.
FIGURE 2.116
Uses of Halogens
Most halogens have a variety of important uses. A few are described in theTable2.11.
TABLE2.11: A Few Uses of Halogens
Halogen Use
Fluorine helps prevent tooth decay, so it is added to
toothpaste as the compound sodium fluoride. You can
learn how it protects teeth at this URL: http://www.a
nimated-teeth.com/tooth_decay/t4_tooth_decay_flu
oride.htm.Chlorine is the active ingredient in household bleach.
It removes stains from clothes. It can also be used to
disinfect countertops and other surfaces.