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Chlorine (Cl)

Last Updated : 09 Nov, 2022
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Chlorine is a chemical element that is represented by the symbol Cl. Chlorine is present in the 17th Group (Halogen Group) and 3rd Period of the Periodic table. Chlorine is the second lightest halogen that lies between Fluorine and Bromine in the halogen group. Chlorine is a yellow-green, pungent-smelling gas at room temperature with an atomic number of 17 and an atomic mass of 35.45. Chlorine is used as a Disinfectant to clean swimming pools etc but is a toxic, corrosive gas that can be irritating to the eyes and respiratory system when coming in direct contact. Let’s Learn more about the element Chlorine in this article.

What is Chlorine?

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 electronic 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 (Cl)


Structure of Chlorine

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 organized into three electron shells: K, L, and M. 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.

Structure of Chlorine


From the above figure, it is clear that the electronic configuration of Chlorine is [Ne] 1s2 2s2 2p6 3s2 3p5 as Chlorine has 17 electrons in it and 7 electrons in its valence shell. 

Electron-dot Structure of Chlorine

Electron-dot Structure of Chlorine


Physical and Chemical Properties of Chlorine

  • Chlorine is a gas and has a greenish-yellow appearance at room temperature and atmospheric pressure.
  • Chlorine is the second halogen element of Group 17 (Halogen Group) of p-block elements with-
    • Atomic Number (Z) or molar mass of Chlorine: 17
    • Atomic Mass of Chlorine: 35.45
    • Boiling Point of Chlorine: 239.11 K
    • Melting Point of Chlorine: 171.6 K
    • Density of Chlorine: 1.5625 g/cm3
    • Electronegativity of Chlorine: 3.16
    • Valency of Chlorine: 1
    • Chemical Formula or Symbol of Chlorine: Cl
  • Chlorine is 2.5 times heavier than air.
  • Chlorine is a highly electronegative and electron affinity element.
  • When charcoal is present, the reaction between Chlorine and Hydrogen occurs quickly in the dark. 
  • Because of its strong affinity for Hydrogen, Chlorine can react with a wide variety of molecules. For example, when Chlorine combines with hydrocarbons, chlorine atoms gradually replace the hydrogen atoms. However, chlorine atoms are easily added to the double or triple bond if the hydrocarbon is unsaturated.
  • Each Chlorine molecule contains two atoms (Cl2). Except for the lighter noble gases, practically all elements interact with chlorine to form Chlorides. 
  • The Chlorides of most metals are ionic crystals, but those of semimetals and nonmetals are primarily molecules.

Isotopes of Chlorine 

The element Chlorine (Cl) has a total of 25 isotopes ranging from 28Cl to 52Cl. Out of these 25 isotopes, only two isotopes are stable. The stable isotopes of Chlorine are 35Cl with 75.77% of abundance and 37Cl which is 24.23% abundant, thus giving chlorine a standard atomic weight of 35.45. The radioactive isotope that lived longest is 36Cl, which has a half-life of 3.01 × 105 years. 

Uses of Chlorine

  1. It is used to eliminate the odor of putrefaction.
  2. It is employed as a disinfectant.
  3. To kill microorganisms, chlorine is utilized 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 utilized in the production of colors and polymers.

FAQs on Chlorine

Question 1: Is Chlorine a metal or a non-metal?


Yes, Chlorine is a metal, it is a yellowish-green gas with a high degree of reactivity. Chlorine reacts with various metals to form a wide range of compounds.

Question 2: Write the electron dot structure for Potassium Chloride.


Since, the number of valence electrons in Potassium (K) and Chlorine (Cl) are 1 and 7, respectively. 

Hence, the electron dot structure for Potassium Chloride is below:

Electron dot structure for Potassium Chloride


Question 3: What happens when Lime Water reacts with Chlorine?


Lime water reacts with chlorine to give Calcium hypochlorite (CaOCl2) or Bleaching Powder as shown in the chemical reaction below:

Question 3


Question 4: Why Bleaching powder gives the smell of Chlorine?


Bleaching powder gives the smell of chlorine because it reacts with the Carbon dioxide present in nature to give Calcium carbonate and Chlorine, as shown in the reaction below:

Question 4


Question 5: 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 6: 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 7: What is chlorination?


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

Question 8: 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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