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Name Chlorine
Atomic Number 17
Atomic Weight 35.453
Symbol Cl
Melting Point ( °C ) -150.7°F (-101.5°C)171.65 K
Boiling Point ( °C ) -29.27°F (-34.04°C)239.11 K
Density (g/cm3) 293 K: 3.214 g/cm3
Earth crust (%) 0.017%
Discovery (Year) 1774
Group 7A
Electron configuration Ne 3s2 3p5
Ionization energy (eV) 12.968 eV

Chlorine has an atomic number of 17 and is located in the family/group 7A known as the halogens. It is a powerful element that can cause medical issues like irritation to the respiratory system, mucus membranes, eyes, and even can burn of the skin etc. It can also be harmful to organisms living in water and in soil. However, this element is used in many everyday products today such as to produce safe drinking water, disinfect swimming pools, found in paper products, textiles, medicines, bleaches, solvents, etc.


Chlorine was discovered in 1774 by Carl Wilhelm Scheele as he combined the mineral pyrolusite (manganese dioxide, MnO2) with hydrochloric acid. He had mistakenly thought that it had contained oxygen, yet it was given its name in 1810 by Humphry Davy who insisted that it was in fact an element. It has an appearance of a greenish yellow dense gas (known as Chloros in Greek) that has a choking smell to it. Its gas is two and a half times as heavy as air and is used to kill bacteria from drinking water supplies. In addition, this diatomic element in nature is found combined with sodium that produces common salt (NaCl), yet dissolves when mixed with water. Chlorides make up much of the salt that is dissolved in the earth's ocean: about 1.9% of the mass of seawater is chloride ions. All in all, Chlorine is an important element that has been useful to people all around the world and companies to produce products we use everyday.


Chlorine has 9 isotopes with mass numbers ranging from Cl-32 to Cl-40. In fact, there are two isotopes that occur naturally which are Cl-35 (75.78%) and Cl-37 (24.22%). These two principal stable isotopes are used to study the toxicity of environmental pollutant and are usually supplied in the form of NaCl.


Two of the most familiar chlorine compounds are sodium chloride (NaCl) and hydrogen chloride (HCl). Sodium chloride, commonly known as table salt, is used to season food and in some industrial processes. Hydrogen chloride, when mixed with water (H2O), forms hydrochloric acid, a strong and commercially important acid.


1. http://www.livescience.com/28988-chlorine.html

2. http://www.rsc.org/periodic-table/element/17/chlorine

3. http://www.icca-chem.org/Portal/SafetySummarySheets/634643784627859023_PSS%20Chlorine_V01.pdf

4. http://www.lenntech.com/periodic/elements/cl.htm#Atomic%20number

5. http://en.wikipedia.org/wiki/Isotopes_of_chlorine

6. http://education.jlab.org/itselemental/ele017.html

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