Iodine is diatomic because each iodine atom needs one more electron to achieve a stable octet configuration. When two iodine atoms bond together, they share two electrons through a covalent bond, resulting in the formation of a stable linear I2 molecule. 1
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Key Takeaways: Why is Iodine Diatomic?
- Iodine is diatomic because each iodine atom needs one more electron to achieve a stable octet configuration.
- Iodine atoms bond through a covalent bond to form a diatomic molecule with the formula I2.
- Monatomic iodine can exist in certain conditions, but it is relatively unstable and highly reactive.
- The bond between the two iodine atoms in I2 is relatively weak and can be broken by supplying energy.
Explanation: Why is iodine a diatomic molecule?
Iodine is a diatomic molecule because it exists naturally as a homonuclear diatomic molecule in its elemental form. In other words, iodine atoms have a strong tendency to bond with each other through a covalent bond, forming a molecule with the formula I2. 2
The reason for this tendency lies in the electronic configuration of iodine atoms. Each iodine atom has seven valence electrons in its outermost shell. In order to achieve a stable electronic configuration with a full outer shell of eight electrons, each iodine atom can share one electron with another iodine atom to form a covalent bond. 3
This sharing of electrons allows both atoms to achieve a stable electronic configuration and a lower energy state than they would have if they existed as separate atoms.
Because of this strong tendency to bond with each other, iodine atoms typically exist as I2 molecules rather than as individual atoms.
This diatomic nature of iodine has important implications in fields such as chemistry and biology, where iodine is commonly used as a reagent or nutrient. 4
Does monatomic iodine exist?
Yes, monatomic iodine can exist in certain conditions, but it is relatively unstable and highly reactive. Monatomic iodine refers to an iodine atom that is not bonded to another iodine atom, but rather exists in its elemental form as a single atom.
Monatomic iodine is usually generated by dissociating iodine molecules, which requires a lot of energy. For example, monatomic iodine can be produced by heating I2 molecules to a very high temperature or by exposing them to ultraviolet radiation. 5
However, once generated, monatomic iodine is highly reactive and tends to quickly react with nearby atoms or molecules in order to form more stable compounds.
For example, monatomic iodine can react with hydrogen gas to form hydrogen iodide (HI) or with oxygen gas to form iodine oxide (I2O). 6 Because of its high reactivity, monatomic iodine is not commonly used in chemical reactions or processes.
How do iodine atoms bond to form a diatomic molecule?
Iodine atoms bond to form a diatomic molecule through a covalent bond. Covalent bonding occurs when atoms share electrons in order to achieve a stable electronic configuration. 7
In the case of iodine, each atom has seven valence electrons in its outermost shell, and requires one more electron to achieve a stable electronic configuration with a full outer shell of eight electrons.
In a diatomic iodine molecule (I2), each iodine atom contributes one electron to a shared pair of electrons, resulting in a single covalent bond between the two atoms. This bond is formed by the overlap of the atomic orbitals of the two iodine atoms, with each atom contributing one electron to the shared bonding orbital.
The bond between the two iodine atoms in I2 is relatively weak and can be broken by supplying energy, such as by heating or by exposure to ultraviolet radiation. 8
When the bond is broken, the resulting atoms are highly reactive and tend to form new bonds with nearby atoms or molecules in order to achieve a more stable electronic configuration.
Further reading
Why is Chlorine Diatomic?
Is Nitrogen a Compound?
Is Oxygen a Compound?
Is Oxygen a Mixture?
Is Water a Mixture?
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References
- P. (n.d.). Iodine. Iodine | I2 | CID 807 – PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/807
- Boudreaux, K. A. (n.d.). The Parts of the Periodic Table. The Parts of the Periodic Table. https://www.angelo.edu/faculty/kboudrea/periodic/physical_diatomics.htm
- Elmhurst.edu http://chemistry.elmhurst.edu/vchembook/150Anpcovalent.html
- Iodine – Wikipedia. (2017, November 20). Iodine – Wikipedia. https://en.wikipedia.org/wiki/Iodine
- Bancroft, W. D., & Morton, D. S. (1929, May 15). MONATOMIC IODINE AND MOLECULAR HYDROGEN. Proceedings of the National Academy of Sciences, 15(5), 438–441. https://doi.org/10.1073/pnas.15.5.438
- Iodine oxide – Wikipedia. (n.d.). Iodine Oxide – Wikipedia. https://en.wikipedia.org/wiki/Iodine_oxide
- I2 Lewis Structure (Iodine Gas). (2022, May 13). YouTube. https://www.youtube.com/watch?v=Gq2NS1fvdOM
- Gardner, J. M., Abrahamsson, M., Farnum, B. H., & Meyer, G. J. (2009, October 22). Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I− Oxidation and I3− Photodissociation. Journal of the American Chemical Society, 131(44), 16206–16214. https://doi.org/10.1021/ja905021c
