Why is Chlorine Diatomic? (+ 3 Facts You Should Know)

Chlorine is diatomic because the two chlorine atoms share electrons to form a stable covalent bond. 1 This arrangement allows the chlorine molecule to have a full outer shell of electrons, making it more stable and less reactive than individual chlorine atoms.

Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.

So let’s dive right into it.

Key Takeaways: Why is Chlorine Diatomic?

  • Chlorine is diatomic because two chlorine atoms share electrons to form a stable covalent bond.
  • Chlorine atoms bond through a covalent bond by sharing a pair of valence electrons to achieve a stable configuration.
  • Monatomic chlorine can exist under certain conditions, but it is highly reactive and unstable.

Explanation: Why is chlorine a diatomic molecule?

Chlorine is a diatomic molecule because it exists in nature as a pair of atoms, which bond together through a covalent bond to form a stable molecule. 2

Chlorine atoms have seven electrons in their outermost energy level, and to become stable, they require one more electron. When two chlorine atoms come together, they share their outermost electrons and complete their outermost energy level, resulting in the formation of a covalent bond.

The covalent bond between the two chlorine atoms is a nonpolar covalent bond because the atoms share the electrons equally. This shared electron pair creates a stable molecule with a symmetric arrangement of the two atoms, giving it a characteristic diatomic structure.

It’s worth noting that not all elements exist as diatomic molecules in nature. 3 For example, noble gases like helium, neon, and argon exist as monatomic gases, meaning they exist as individual atoms and not as pairs. 4 5

Does monatomic chlorine exist?

Yes, monatomic chlorine can exist, but only under certain conditions. 6 In general, chlorine exists as a diatomic molecule (Cl2) because the two chlorine atoms form a stable covalent bond. However, at high temperatures and low pressures, chlorine molecules can dissociate into individual chlorine atoms, leading to the formation of monatomic chlorine (Cl).

For example, in a high-temperature flame, such as that of a gas burner or a welding torch, chlorine molecules can dissociate into chlorine atoms due to the high temperatures.

Similarly, in the upper atmosphere, solar radiation can cause the dissociation of chlorine molecules, leading to the formation of monatomic chlorine. 7 8

However, monatomic chlorine is highly reactive and unstable. It can react quickly with other molecules to form new compounds, making it difficult to isolate and study.

Additionally, in normal atmospheric conditions, the concentration of monatomic chlorine is very low compared to diatomic chlorine.

How do chlorine atoms bond to form a diatomic molecule?

Chlorine atoms bond to form a diatomic molecule through a covalent bond, which involves the sharing of a pair of valence electrons between the two atoms. 9

Specifically, each chlorine atom has seven valence electrons, which are the outermost electrons in its electron shell. To achieve a stable configuration, each chlorine atom needs one more electron, so the atoms can share a pair of electrons, with each atom contributing one electron to the pair. 

This results in the formation of a single covalent bond between the two atoms, creating a stable diatomic molecule of chlorine (Cl2).

This shared electron pair holds the two atoms together, with each atom being attracted to the shared electrons and held in place by electrostatic forces.

Further reading

Is Nitrogen a Compound?
Is Oxygen a Compound?
Is Oxygen a Mixture?
Is Water a Mixture?
Why is Oxygen a Pure Substance? 

About author

Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.

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  1. Diatomic molecule – Wikipedia. (2007, August 24). Diatomic Molecule – Wikipedia. https://en.wikipedia.org/wiki/Diatomic_molecule
  2. Covalent Bonding. (2013, October 3). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Chemical_Bonding/Fundamentals_of_Chemical_Bonding/Covalent_Bonding
  3. 5.2: Monotomic and Diatomic Elements. (2022, January 24). Chemistry LibreTexts. https://chem.libretexts.org/Courses/Portland_Community_College/CH151%3A_Preparatory_Chemistry/05%3A_The_Nuclei_of_Atoms/5.02%3A_Monotomic_and_Diatomic_Elements
  4. Monatomic gas – Wikipedia. (2016, June 6). Monatomic Gas – Wikipedia. https://en.wikipedia.org/wiki/Monatomic_gas
  5. Group 18: Properties of Nobel Gases. (2015, May 18). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_and_Websites_(Inorganic_Chemistry)/Descriptive_Chemistry/Elements_Organized_by_Block/2_p-Block_Elements/Group_18%3A_The_Noble_Gases/1Group_18%3A_Properties_of_Nobel_Gases
  6. P. (n.d.). Chlorine atom. Chlorine Atom | Cl | CID 5360523 – PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/5360523
  7. Acker, J., Williams, R., Chiu, L., Ardanuy, P., Miller, S., Schueler, C., Vachon, P., & Manore, M. (2014). Remote Sensing from Satellites☆. Reference Module in Earth Systems and Environmental Sciences. https://doi.org/10.1016/b978-0-12-409548-9.09440-9
  8. ACS https://www.acs.org/education/whatischemistry/landmarks/cfcs-ozone.html
  9. Cl2 Lewis Structure – How to Draw the Dot Structure for Cl2. (2013, May 4). YouTube. https://www.youtube.com/watch?v=QFp52sItL50

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