Chemical Properties of Phosphorus Trichloride

Oct 13, 2025 by leolavanderia.com.br 108 views

Introduction

Phosphorus trichloride, $PCl_3$ , is a chemical compound that consists of phosphorus and chlorine atoms. It is a colorless, oily liquid with a pungent odor. In this article, we will explore the correct Lewis structure for $PCl_3$ and discuss the factors that determine its structure.

What is a Lewis Structure?

A Lewis structure is a diagram that represents the arrangement of electrons in a molecule. It is a two-dimensional representation of the molecule, showing the bonds between atoms and the lone pairs of electrons. Lewis structures are named after Gilbert N. Lewis, who first proposed them in the early 20th century.

Drawing a Lewis Structure

To draw a Lewis structure, we need to follow a series of steps. First, we need to determine the total number of valence electrons in the molecule. Valence electrons are the electrons in the outermost energy level of an atom. For $PCl_3$ , the phosphorus atom has 5 valence electrons, and each chlorine atom has 7 valence electrons. Therefore, the total number of valence electrons in $PCl_3$ is 5 + 3(7) = 26.

Factors that Determine the Lewis Structure

There are several factors that determine the Lewis structure of a molecule. These include:

Electronegativity: Electronegativity is the ability of an atom to attract electrons in a covalent bond. Atoms with high electronegativity values tend to attract electrons more strongly than atoms with low electronegativity values.
Bond order: Bond order is a measure of the number of electrons in a bond. A higher bond order indicates a stronger bond.
Lone pairs: Lone pairs are pairs of electrons that are not involved in bonding. They are typically found on atoms that have a high number of valence electrons.

Possible Lewis Structures for $PCl_3$

There are several possible Lewis structures for $PCl_3$ . These include:

Structure 1: In this structure, the phosphorus atom is bonded to three chlorine atoms, with no lone pairs on the phosphorus atom.
Structure 2: In this structure, the phosphorus atom is bonded to two chlorine atoms, with one lone pair on the phosphorus atom.
Structure 3: In this structure, the phosphorus atom is bonded to one chlorine atom, with two lone pairs on the phosphorus atom.

Which Structure is Correct?

To determine which structure is correct, we need to consider the factors that determine the Lewis structure. In this case, the electronegativity of the chlorine atoms is higher than that of the phosphorus atom. Therefore, the chlorine atoms will attract electrons more strongly than the phosphorus atom.

Conclusion

In conclusion, the correct Lewis structure for phosphorus trichloride, $PCl_3$ , is Structure 1. This structure shows the phosphorus atom bonded to three chlorine atoms, with no lone pairs on the phosphorus atom. The electronegativity of the chlorine atoms is higher than that of the phosphorus atom, which explains why the chlorine atoms attract electrons more strongly.

References

Gilbert N. Lewis: Lewis, G. N. (1916). "The Atom and the Molecule." Journal of the American Chemical Society, 38(4), 762-785.
Phosphorus Trichloride: Phosphorus trichloride. (n.d.). In Wikipedia. Retrieved from https://en.wikipedia.org/wiki/Phosphorus_trichloride

Additional Resources

Lewis Structures: Lewis structures. (n.d.). In Chemistry LibreTexts. Retrieved from https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_(Zumdahl)/Chapter_03%3A_Chemical_Bonding_I%3A_The_Bonding_Theories/3.3%3A_Lewis_Structures
Electronegativity: Electronegativity. (n.d.). In Chemistry LibreTexts. Retrieved from https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_(Zumdahl)/Chapter_04%3A_Electrochemistry/4.1%3A_Electronegativity

Introduction

In our previous article, we discussed the correct Lewis structure for phosphorus trichloride, $PCl_3$ . In this article, we will answer some frequently asked questions about $PCl_3$ .

Q: What is the molecular formula of phosphorus trichloride?

A: The molecular formula of phosphorus trichloride is $PCl_3$ .

Q: What is the molar mass of phosphorus trichloride?

A: The molar mass of phosphorus trichloride is 137.32 g/mol.

Q: What is the boiling point of phosphorus trichloride?

A: The boiling point of phosphorus trichloride is 76.1°C.

Q: What is the melting point of phosphorus trichloride?

A: The melting point of phosphorus trichloride is -94.5°C.

Q: Is phosphorus trichloride a polar molecule?

A: Yes, phosphorus trichloride is a polar molecule due to the difference in electronegativity between the phosphorus and chlorine atoms.

Q: What is the dipole moment of phosphorus trichloride?

A: The dipole moment of phosphorus trichloride is 1.02 D.

Q: Is phosphorus trichloride a toxic substance?

A: Yes, phosphorus trichloride is a toxic substance and can cause irritation to the skin, eyes, and respiratory system.

Q: How is phosphorus trichloride used in industry?

A: Phosphorus trichloride is used in the production of various chemicals, including phosphoric acid, phosphorus pentachloride, and other phosphorus compounds.

Q: Can phosphorus trichloride be used as a fuel?

A: No, phosphorus trichloride is not a suitable fuel due to its high reactivity and toxicity.

Q: Is phosphorus trichloride a good solvent?

A: No, phosphorus trichloride is not a good solvent due to its high reactivity and toxicity.

Q: Can phosphorus trichloride be used in the production of pharmaceuticals?

A: Yes, phosphorus trichloride can be used in the production of certain pharmaceuticals, but it requires careful handling and safety precautions.

Q: Is phosphorus trichloride a stable compound?

A: No, phosphorus trichloride is a reactive compound and can decompose or react with other substances under certain conditions.

Conclusion

In conclusion, phosphorus trichloride, $PCl_3$ , is a toxic and reactive compound that requires careful handling and safety precautions. It has various industrial applications, including the production of phosphoric acid and other phosphorus compounds. However, it is not a suitable fuel or solvent due to its high reactivity and toxicity.

References

Phosphorus Trichloride: Phosphorus trichloride. (n.d.). In Wikipedia. Retrieved from https://en.wikipedia.org/wiki/Phosphorus_trichloride
Chemical Properties of Phosphorus Trichloride: Chemical properties of phosphorus trichloride. (n.d.). In Chemistry LibreTexts. Retrieved from https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_(Zumdahl)/Chapter_04%3A_Electrochemistry/4.1%3A_Electronegativity
Toxicity of Phosphorus Trichloride: Toxicity of phosphorus trichloride. (n.d.). In PubChem. Retrieved from https://pubchem.ncbi.nlm.nih.gov/compound/Phosphorus-trichloride

Additional Resources

Phosphorus Trichloride: Phosphorus trichloride. (n.d.). In Sigma-Aldrich. Retrieved from https://www.sigmaaldrich.com/catalog/product/sigma/pcl3
Chemical Safety: Chemical safety. (n.d.). In OSHA. Retrieved from https://www.osha.gov/chemical-safety