Photo Credit: Periodic Table
Atomic Number: 17
Relative Atomic Mass: 35.45
Group: 17
Period: 3
Block: P

Symbol: Cl

Chlorine is a non-metal which is gas at room temperature. Chlorine is a yellowy-green gas which has a choking smell. 40 million tonnes of gas are made yearly by the process Electrolysis of brime. It is toxic. Therefore, it has been used as a chemical weapon in the First World War. Chlorine caused irritation in the airway, leading to pulmonary oedema (UK spelling) in humans. Pulmonary Oedema is an excessive build-up of fluid in the lungs which causes breathing difficulties... Yeah, not pleasant!

Chlorine is also the second-lightest halogen after Fluoride.

Halogen - is a highly reactive group of elements within the periodic table, based at Group 17. There are five elements within this group; Fluorine, Chloride, Bromide, Iodine and Astatine.

Chlorine is naturally combined. The compound Halite, otherwise called Sodium Chloride or Salt, is the main mineral which is mined for the element. But, Salt is soluble. The Sodium chloride has leeched into the oceans from land and salt beds, or ancient lakes, can be also mined for chlorine.

Photo Credit: Britannica
The Discovery of Chlorine

Chlorine was discovered in the year 1774 by the Swedish chemist named as Carl Wilhelm Scheele (Pictured left). Though hydrochloric acid (HCl) known to the alchemists already. But, it was the gaseous element form which was identified by Carl Wilhelm Scheele. It was isolated by heating hydrochorlic acid with the mineral - pyrolusite, which is a naturally occuring Manganese Dioxide (MnO₂). A dense, greenish-yellow gas was formed. Carl Wilhelm Scheele recorded Chlorine of having a choking smell and disolved within water to form an acid. The element bleeched litmus paper and discoloured leaves.
But, the chemist believed that he had created Oxygen. Not Chloride.

But, Carl Wilhelm Scheele wasn't the only chemist who tried to isolate Chlorine. Sir Humphry Davis also investigated it in the year 1807. It was eventually concluded that Chlorine wasn't just a simple substance - It was an element. Sir Humphry Davis announced this news in 1810. But, chlorine wasn't accepted as an element until 10 more years for some to accept the fact.

Biological Uses

Even though chlorine is toxic. The ion is essential to life. The ion is mostly present within the fluid of the cell as a negative ion in order to balance the positive ion of the cell (Mostly potassium ion). Chlorine is also within extra-cellular body fuild such as blood to balance the positive (sodium) ion.

We get most of our chloride ion through salt - Sodium Chloride. The typical intake is 6g. But, we only need half of that.

Photo Credit: Royal Society of Chemisty
It's Uses

  • Chlorine is used as a disinfectant - It kills bacteria. 
    • It is used to treat swimming pools and drinking water. 
    • To make hunderds of products from insectide to paint
  • 20% of Chloride is used to produce PVC. A versatile plastic which is used in window frames, electrical wiring, water pipes, blood bags and vinyl flooring.
  • Used in Organic chemistry. It is an oxidising agent.
    • 85% of pharmaceutals use chlorine at some stage
  • Very posionous - Chlorine was used as a weapon during the First World War