Atoms and Molecules - Periodic Table

The halogens are located in Group VII, now known as Group 17, of the periodic table. Included in the halogen family are the elements fluorine, chlorine, bromine, iodine, and astatine (F, Cl, Br, I, and At, respectively). Halogens are fairly reactive due to their seven valence electrons. They are very close to the desired octet, and easily pick up one electron. Due to their reactivity, halogens are only found in nature when they are in a molecular compound. Fluorine and chlorine are gases at room temperature. Bromine is a liquid at room temperature, and iodine and astatine are solids at room temperature.


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The halogens were named by a Swedish chemist by the name of Jöns Jakob Berzelius. Halogen means "salt come to be" and is significant because halogens form salts when reacted with metals.


Real World Application

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Fluorine is used in non-stick Teflon pans. Fluorine is also used to etch glass and is an ingredient in toothpaste.  CFCs, or chlorofluorocarbons, are a main component in refrigeration and cooling units. Fluorine has been added in very small quantities to public water supplies to reduce tooth decay.


The use of chlorine is quite common. You may recognize the smell of chlorine in public swimming pools or bleach. This is because chlorine makes an excellent disinfectant. One of the most common applications of chlorine is in something that you ingest every day:  table salt is NaCl.


Bromine is used as a pesticide. It is also used to flame-proof things. Bromine, like chlorine, is commonly used in disinfectants and sanitizers.


Iodine use is very important to the medical community. This is due to its antiseptic qualities. Iodine is often added to halogen headlights that are used in vehicles. 


Astatine is radioactive and has no known real world applications.



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 Important Vocabulary

Term Context



Browse relevant videos from the Journal of Chemical Education's (JCE) Chemistry Comes Alive! library and other video sources.

Chlorine with Acid

Test Tube One and Two:

Test Tube Three and Four:

Comparing the Four Halogens

The reactions in this video are:

F2(g) + Fe(s) → FeF3

F2(g)+ C(s) → CF4

F2(g) + H2(g) → 2HF (g)

H2(g) + Cl2(g) → 2HCl(g)

HCl(g)+ H20(l) → H3O+ + Cl-

2Al(s) +3 F2(g) → 2AlF3

2Al(s) +3 Cl2(g) → 2AlCl3

2Al(s) + 3Br2(g) → 2AlBr3

2Al(s) + 3I2(g) →2 AlI3


Computer Animations

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