THE PERIODIC TABLE

4.2 - The Groups

The halogens: F, Cl, Br, I, and At

View the halogen.

Physical Properties:	fluorine, a pale yellow gas chlorine, a greenish gas, has an irritating odor bromine, a red-brown liquid at room temperature iodine, a dark grey crystalline solid at room temperature
Chemical Properties:	the halogens exist as diatomic gas molecules (section 4.7) all halogens have seven valence electrons (section 3.3) which form ions with a negative (-1) charge fluorine is the most reactive of all the nonmetals iodine sublimes (section 2.1) when heated
Abundance:	bromine is obtained by processing brine from wells and from seawater iodine is obtained from brine wells and sea plants such as kelp astatine is radioactive. Less than 30 grams exist in the Earth's crust. For greater quantities, this element needs to be synthesized in a laboratory.
Common Compounds and Usages:	fluorine is the source to produce fluorocarbons such as Freon-12, that are still used as refrigerants in air conditioners. fluorine is a key ingredient in teflon, a fluorocarbon polymer chlorine, in low level, is used to purify drinking water. In high concentrations, it is poisonous chlorine is used in production of paper, textiles, bleaches, medicines, insecticides, paints, plastics bromine is used in photographic chemicals, dyes, fire retardants and in pharmaceutical products iodine compounds are used in producing iodized salt, photographic chemicals and in medicines iodine is required in human body in order to make the hormone thyroxin

Follow this interesting link to see more pictures of the elements:

The Pictorial Periodic Table from Phoenix College

Section 5.2
The Periodic Table Periods and Groups ..p106

Section 5.3
General Characteristics of the Groups ..p109

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