2.55. Halogens http://www.ck12.org
2.55 Halogens
- Identify halogens.
- Describe physical and chemical properties of halogens.
- List some uses of halogens.
You’ve probably seen halogen lights like the ones pictured here. You may even have halogen lights in your home. If
you do, you may have noticed that they get really hot and give off a lot of light for their size. A halogen light differs
from a regular incandescent light bulb in having a small amount of halogen gas inside the bulb. The gas combines
chemically with the metal in the filament, and this extends the life of the filament. It allows the lamp to get hotter and
give off more light than a regular incandescent light without burning out quickly. What is halogen gas, and which
elements are halogens? In this article, you’ll find out.
Meet the Halogens
Halogensare highly reactive nonmetallic elements in group 17 of the periodic table. As you can see in the periodic
table shown in theFigure2.115, the halogens include the elements fluorine (F), chlorine (Cl), bromine (Br), iodine
(I), and astatine (At). All of them are relatively common on Earth except for astatine. Astatine is radioactive and
rapidly decays to other, more stable elements. As a result, it is one of the least common elements on Earth.
Q:Based on their position in the periodic table from theFigure2.115, how many valence electrons do you think
halogens have?
A:The number of valence electrons starts at one for elements in group 1. It then increases by one from left to right
across each period (row) of the periodic table for groups 1–2 and 13–18. Therefore, halogens have seven valence
electrons.