Chlorine- Electron configuration, Atomic number, Mass, Uses

What is Chlorine?

Chlorine takes its name from the color of its gas, which is a little greenish. In ancient Greek, "khlôros" meant a slightly greenish yellow.

Chlorine is an important component of plant and animal tissues, present mainly in the form of an ion due to the dissociation of sodium, potassium, calcium, magnesium salts, etc.

The largest presence of chlorine in its natural state is combined in the salt, sodium chloride, of the formula NaCl. It can also be found in certain mineral species such as sylvite and carnallite.

Chlorine Symbol

It is represented by its symbol Cl. In its pure state and maintaining its normal conditions, it creates dichlor, which is a toxic gas that is much heavier than air and has a very unpleasant odor.

Chlorine Atomic Number

Chlorine is a very abundant chemical element in nature and is part of the periodic table, which is distinguished by having an atomic number of 17, and being located in group VIIA, which corresponds to the halogens.

We can say Chlorine is a chemical element that has atomic number 17 in the periodic table of elements.

Atomic Mass of Chlorine 

Chlorine is the most abundant halogen in the earth's crust, most often in the form of two isotopes. Due to its chemical activity, it is found only in the form of compounds of many minerals.

The atomic mass of the element is 35.453 u. It is denoted by the symbol Cl (from Latin Chlorum). Chlorine is a reactive nonmetal that belongs to the halogen group.

General properties of Chlorine

Symbol of Chlorine


Chlorine Atomic number










Volumic mass





Green yellow

Atomic properties of Chlorine

Chlorine Atomic mass


Atomic radius of Chlorine

100 pm

Electronic configuration of Chlorine

[Ne] 3s2 3p5

Electrons per energy level

2 | 8 | 7


strong acid

Chlorine Physical properties

ordinary state


Fusion point


Boiling point


Who discovered Chlorine?

The first man to isolate chlorine was a Swedish chemist named Carl Wilhelm Scheele. This discovery took place in 1774. It was by pouring a few drops of hydrochloric acid on manganese dioxide that the reaction occurred.

This was obtained by carrying out the following reaction:

MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O

He first called this gas dephlogisticated muriatic acid, thinking at first of a compound gas. It was actually about chlorine. 

Carl Wilhelm Scheele also  discovered many chemical compounds such as oxygen, glycerin or even chlorine.

This was used in the manufacturing of certain chemical weapons in World War I due to its high level of toxicity.

Chlorine Electron Configuration

Electronic configuration of Chlorine in detail is: 1s2 2s2 2p3s2 3p5 , also you can write chlorine electron configuration in abbreviated form i.e. [Ne] 3s2 3p5.

The chlorine atom and P-2 , S-1 have the same electronic configuration.

Chlorine has 17 electrons, we can fill the electron shells in the order as below::

  • 2 electrons per 1s sublevel
  • 2 electrons per 2s sublevel
  • 6 electrons per 2p sublevel
  • 2 electrons per 3s sublevel
  • 5 electrons per 3p sublevel

Chlorine electronic configuration comes to determine the way in which its electrons are structured. In this case chlorine has a mean radius of 100 pm, a Van der Waals radius of 175 pm, a covalent radius of 99 pm, and the Bohr or atomic radius is 79 pm.

What is the oxidation state of Chlorine?

Chlorine atoms in compounds have oxidation states 6, 5, 4, 3, 2, 1, 0, -1, -2.

What is the Ionization energy of chlorine?

The Ionization energy of chlorine, E o = 1251 kJ/mol.

What are the quantum numbers of chlorine?

Quantum numbers are determined by the last electron in the configuration; for chlorine atoms, these quantum numbers have the value N = 3, L = 1, Ml = 0, Ms = ½ .

What is the valency of chlorine?

The chlorine valence characterizes the ability of the Cl atom to form chemical bonds. Chlorine atoms in compounds exhibit valence VI, V, IV, III, II, I.

Isotopes of Chlorine

Chlorine has 24 isotopes known to date, their mass number varying from 28 to 51. Its two main isotopes present are stable, they are chlorine 34 and chlorine 38. Its most stable radioisotope with the longest duration of half-life is chlorine-36 which has a half-life of 310,000 years.

As for the others, their half-life varies between a few minutes and a few seconds. For example, there is chlorine 29 which has a half-life of 20 nanoseconds or chlorine 30 which has a half-life of 30 nanoseconds.

Physical and chemical properties of the element Cl

  • Pure chlorine is in the form of a gas, dichlor with the formula Cl2 .
  • It can be made liquid by dropping below -34°C.
  • Chlorine is a very reactive molecule, which means that it can easily react with other molecules. This is the case for all the elements belonging to the group of halogens, such as chlorine.
  • This element has diatomic molecules that are chemically active.
  • Being in a dry state, it is considered an inert element, but when it goes into a wet state, it combines directly with other elements, thus forming various compounds.
  • It is therefore easy to dissolve chlorine in water. At 10°C and normal atmospheric pressure, it is possible to dissolve 3.10 L of chlorine in 1 L of water. The higher the temperature, the less easily it dissolves. For example, once it reaches 30°C, it is only possible to dissolve 1.77 L of chlorine in 1 L of water.

What are the uses of Chlorine?

  • The main use of chlorine is that which takes advantage of its biocidal properties.
  • Chlorine is used as a biocide, i.e. to kill bacteria. It is also used as a laundry bleacher.
  • Chlorine is added to public water to kill bacteria and germs in the pipes.
  • Chlorine is part of the composition of bleach, a disinfectant that is used to purify and therefore make water drinkable.
  • It is also used in medicine to produce antiseptics or medicines, but also as pesticides.
  • In geology, one of its isotopes, chlorine 36, which comes from cosmic rays, is used to date surfaces or calculate their erosion.
  • Chlorine is frequently used as an oxidant or as a substitute for hydrogen.
  • It is also dissolved in swimming pools in the form of chloro-isocyanurates for shock chlorine treatments and in the form of trichloroisocyanuric acid for slow chlorine cures, both of which come in solid form, which is easier to use.

Effects of Chlorine-

  • Prolonged exposure to chlorine can cause respiratory problems, such as asthma or allergies.
  • Indeed, chlorine has an irritating effect on the respiratory tract by destroying those of Clara, cells having a protective effect on the lungs.
  • It has been proven that people who often breathe pool water are more prone to these pathologies.
  • An increase in the level of chlorine in the blood occurs with dehydration, impaired renal excretory function, diabetes insipidus, respiratory alkalosis, adrenal insufficiency.

Know about more periodic elements- Gadolinium, Germanium Atomic Number, Neon, Promethium, Selenium, Terbium, Tellurium, Yttrium, Ytterbium Atomic Mass, Zirconium

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