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Chlorine – Occurrence, Structure, Properties, Uses

  • Last Updated : 29 Dec, 2021

Chlorine takes on the appearance of pale yellow-green gas. Chlorine in liquid form can burn the skin, and chlorine in gaseous form irritates the mucous membrane. On the periodic table, it is found between fluorine and bromine. It has a [Ne] 3s2 3p5 electrical configuration. The stable isotopes of chlorine are one and two. Sodium chloride is the most common chlorine chemical, while hydrogen chloride is the most basic. Sodium chloride has the molecular formula NaCl, whereas hydrogen chloride has the molecular formula HCl. It has high reactivity. Chlorine was discovered in 1774 by Carl Wilhelm Scheele, a Swedish scientist.

Chlorine, abbreviated as Cl, is the second lightest halogen. This chemical element has an atomic number of 17.

Chlorine was used extensively in mediaeval alchemists’ experiments, which typically involved heating chloride salts such as ammonium chloride and common salt to produce various chlorine-containing chemical substances such as hydrogen chloride, mercury (II) chloride, and hydrochloric acid in the form of aqua regia.

Because of its high reactivity, all chlorine in the Earth’s crust is in the form of ionic chloride compounds, which include table salt. In the Earth’s crust, it is the second most plentiful halogen and the twenty-first most prevalent chemical element. Despite this, the vast quantities of chloride in seawater dwarf these crustal deposits.

Occurrence and distribution of Chlorine 

Except for very minute amounts of free chlorine in volcanic gases, chlorine is exclusively found in chemical compounds. It makes up 0.017 percent of the Earth’s crust. The two stable isotopes of chlorine make up natural chlorine. Sodium chloride is the most prevalent chlorine compound, which is found in nature as crystalline rock salt that is often coloured by impurities. Sodium chloride is also found in saltwater, which has a sodium chloride content of roughly 2%. Blood and milk both contain trace amounts of sodium chloride. Evaporite minerals like chlorapatite and sodalite contain it. In the stomach, there is free hydrochloric acid.

Evaporation of prehistoric seas must have generated today’s salt deposits, with the salts having the least solubility in water crystallising first, followed by those with greater solubility. Because potassium chloride is more soluble in water than sodium chloride, a layer of potassium chloride was applied to certain rock salt formations. To get to the sodium chloride, the potassium salt, which is useful as a fertiliser, must first be removed.

Properties of Chlorine 

Chlorine, a nonmetal in group 17, is the second halogen in the periodic table. As a result, its properties are comparable to those of fluorine, bromine, and iodine, and fall somewhere in between the first two. Chlorine has the electron configuration [Ne] 3s2 3p5, with seven electrons in the third and outermost shell serving as valence electrons. It is one electron shy of a full octet, like all halogens, and hence a potent oxidising agent, interacting with other elements to complete its outer shell.

The electronegativity of this element lies somewhere between fluorine and bromine. In accordance with periodic patterns, this element is less reactive than fluorine and more reactive than bromine. It is a greater oxidising agent than bromine, despite being a lesser oxidising agent than fluorine. In comparison to bromide, the chloride ion is a lesser reduction agent, although it is more powerful than fluoride.


Chlorine has an atomic number of 17. This means that chlorine’s atomic structure has a total of 17 protons and 17 electrons. These electrons are organised into three electron shells: primary, secondary, and tertiary. Chlorine has two electrons in its first electron shell and eight electrons in its second electron shell. Finally, the chlorine atom’s outermost electron shell (also known as the valence shell) has a total of 7 electrons. As a result, the valency of chlorine is frequently assumed to be 7. It’s worth noting, though, that chlorine only requires one more electron to complete its octet structure. As a result, the valency of chlorine can also be thought of as 1.


  1. It is used to eliminate the odour of putrefaction.
  2. It is employed as a disinfectant.
  3. To kill microorganisms, chlorine is utilised in the treatment of drinking water.
  4. It is employed in the cleaning of swimming pools.
  5. It is used in the manufacture of paper and paper-related products.
  6. It is employed as an antiseptic.
  7. It is used in the manufacture of medicines.
  8. It’s utilised in the production of colours and polymers.

Sample Questions

Question 1: Is chlorine volatile?


Although chlorine is unstable as a result of relatively unlikely secondary exposure from exposed individuals, chlorine gas can condense on the skin and infect others via dermal contact.

Question 2: Why is chlorine gas Green?


Chlorine is a yellow-green gas at room temperature. Chlorine has a strong, unpleasant, bleach-like odour that can be perceived even at low concentrations. Because the chlorine gas concentration is approximately 2.5 times that of air, it will initially remain close to the ground in locations with low air movement.

Question 3: Is chlorine a poisonous gas?


Gaseous chlorine is toxic and is classified as a lung irritant. It has an intermediate water solubility and the ability to produce acute harm to the upper and lower respiratory tracts. Chlorine gas is immediately detectable due to its strong odour.

Question 4: What is chlorination?


Chlorination is a typical chemical treatment used to destroy bacteria in water.

Question 5: What is the valency of chlorine?


In its atomic structure, chlorine has 17 protons and 17 electrons. These electrons are organised into three basic electron shells. The first electron shell has two electrons, whereas the second electron shell has eight electrons. Finally, there are 7 electrons in the valence shell. As a result, the valency of chlorine is frequently assumed to be 7. 

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