2. Chlorines symbol is Cl.Chlorine is also used in pools, plastics,medicines,paper,textiles,paint and many more.

3. SymbolCI Atomic Number17 Atomic Mass34.968852721 Melting Point172.17 Boiling Point239.18 FamilyHalogens Density3.21 Standard StateGas # of electrons in outer shell7 Used in pools,deadly gas,plastics,paper

4. Chlorine was dicovered in 1774 by a man named Carl William Scheele was mixing pyrolusite and hydrocholic acid together which formed a greenish yellow gas with a suffocating scent.He called it chlorine.

5. Chlorine is a green reactive gas,found in seawater and lakes. It strongly attaches to elements such as oxygen and can only be liberated by using other elements such as oxide or potassium dichromate. Chlorine is also extremely explosive.These characteristics make it useful in pools because it effectively kills bacteria.

6. Iodine is used to prevent thyroid gland problems and is an excellent germ killer. Fluoride is used to strengthen teeth. Bromine was used as an additive to leaded gasoline and can be used for photographic film..

7. Chorine is used in pools because it kills bacteria inside the pool. chlorine was used as a deadly gas in World War One because it suffocated their enemies.. Polyhexanethylene is a non-chlorine alternative for swimming pools. It is effective because it fights microorganisms, it’s not effected by Ultra violet rays like chlorine and can withstand temperature changes

8. http://www.howstuffworks.com Brian KnappElements Of Chlorine,Grolier Educational, Sherman Turnpike 1996,4-7,Danbury,Cnnecticut DavidE.NewtonChemicalElements,U.X.L 199419-22,Farmington Hills

9. Chlorine