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PCl5 Hybridization - Lewis Structure, Structure, Geometry FAQs

PCl5 Hybridization - Lewis Structure, Structure, Geometry FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:45 PM IST

Hybridization is defined as the formation of a new degenerate orbital by mixing two atomic orbitals having the same energy. These hybrid orbitals have different shapes and energies than the original atomic orbitals. which is used to explain the bonding and geometries.

In this article, we will cover the concept of Hybridization. This concept falls under the broader category of Chemical Bonding which is a crucial chapter in Class 11 chemistry. It is not only essential for board exams but also for competitive exams like the Joint Entrance Examination (JEE Main), National Eligibility Entrance Test (NEET), and other entrance exams such as SRMJEE, BITSAT, WBJEE, BCECE, and more.

This Story also Contains
  1. PCl5 Hybridization
  2. Some Solved Examples
  3. Summary

PCl5 Hybridization

Compound PCl₅ comprises of phosphorus and chlorine in the ratio of P: Cl = 1:5. PCl₅ can exist in both solid and gaseous states but is generally found in gaseous states. In a solid state, it will be in charged form. As we know phosphorus belongs to the 3rd period in the modern periodic table. In the third period, there are s, p, and s subshells are present. So in PCl₅ molecule hybridization of p will be sp3d. This hybridization of p in PCl₅ is possible due to the presence of d orbital in phosphorus. If we talk about energy then for the 15th group elements like nitrogen, phosphorous (p), arsenic (Ar), antimony (Sb), and bismuth ( Bi) will be in the order:-

  1. The energy of 3d ~ energy of 3s ~ energy of 3p as well as e energy of 3d ~ energy of 4s ~ energy of 4p.

Because of the above reason hybridization of 3rd-period elements include 3d, 3p, and 3s or 3d, 4s, and 4p ( as the energy of s and p is equivalent to d) and there is also an energy difference between 3p and 4s orbital which led to no hybridization of an element with 3p, 3d and 4s.

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PCl5 hybridization

The hybridization of PCl₅ is sp3d.

PCl5 shape

PCl5 shape is trigonal bipyramidal.

PCl5 geometry

The molecular geometry of is PCl5 trigonal bipyramid.

PCl5 structure

PCl5 structure

PCl5 lewis structure

PCl5  lewis structure

Some of our important hybridization including s, p, and d orbital are given below:-

• Shape of molecules

• Types of hybridization

• Atomic orbitals

• Example

  • Square planar

dsp2

d+s+p(2)

[Ni(CN)4]2–

  • Trigonal bipyramidal

sp3d

s+p(3)+d

PCl5

  • Square pyramidal

sp3d

s+p(3)+d

BrF5

  • Octahedral

Sp3d2, d2sp3

s+p(3)+d(2), d(2)+s+p(3)

[CrF6]3–, [Co(NH3)6]3+








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Some Solved Examples

Q- 1 Is PCl6 hybridization possible?

Ans: PCl6 hybridization will not be possible because of the presence of only 5 valence electrons in the case of phosphorus. The valency of phosphorus is -3 as it will accept 3 electrons from any other elements to complete its octet and be stable. So PCl6 is not possible as the formation of PCl6 phosphorus must contain 6 valence electrons then it can form 6 bonds which include coordinating bonds or covalent bonds. But it is not possible in group 3 elements. Because in the modern periodic table group numbers represent the valency and no. of valence electrons in any elements we can get through its electronic configuration. And in 3rd period elements here in the case of phosphorus, there are only 5 valence electrons available.

Q – 2 Explain the hybridization involved in phosphorus pentachloride.

Ans: The hybridization involved in P of PCl₅ is 5 sp³d.

Q –3 Explain the formation of PCl₅?

Ans: Here we know that outermost electrons or valence electrons are 5 in the case of phosphorus and the orbits are 1s, 3p, and 1d i..e.. available for hybridization. And the hybridization of PCl₅ will be sp3d and we will get a set of 5 hybrid orbitals. So we can represent its hybridization as 5 sp3d and the no. 5 also represents us about its shape as its shape has five corners and i..e.. also true for trigonal bipyramidal. And the shape of PCl₅ will be trigonal bipyramidal, we are helpful for VSEPR theory due to which we can get to know about the molecular shape and its hybridization.

As we know trigonal bipyramidal is a closed figure so there must be bond angles we can discuss and the amazing fact is that not all the bond angles in PCl₅ hybridization i..e.. trigonal bipyramidal is the same, and in this geometry, we can also notice that orbitals of phosphorus i.e. in hybridization and will become sp3d orbital will overlap with p orbital of chlorine and this results in the formation of p-cl bond which counts for 5 in number.

Q –4 PCl₅ shape according to VSEPR theory?

Ans: According to VSEPR theory shape of PCl₅ is trigonal bipyramidal and its hybridization in the gaseous state is sp³d but in solid state its hybridization will be changed to sp³d² and sp³.

Q-5 How many types of bonds are formed in PCl₅?

Ans: Types of a bond will be 2, there are two types of bond that will be formed during molecule formation i.e. PCl₅ formation and the bonds are equatorial bonds and the other one is axial bonds. The number count for the axial bond is 2 and the number count for the equatorial bond is 3. And these both types of bonds are p – cl bonds indicating that there are 3 p – cl bonds in the equatorial plane and 2 p – cl bonds lie in the axial plane.

Q - 6 What are the bond angles of both equatorial bonds and axial bonds?

Ans: • Equatorial bonds i.e. all 3 p – cl bonds which lie in the same plane. They are arranged by making an angle of 120°.

• Axial bond i..e.. all 2 p – cl bonds in which one p – cl bond lies above the equatorial surface and the other one p – cl bond lies below the equatorial plane. These both p – cl bonds make an angle of 90° with p – cl bonds situated in an equatorial plane or equatorial bond. The angle between both p – cl bonds in axial position is 180° as they are situated just opposite to each other

Q –7 Which bond is weaker equatorial or axial?

Due to repulsive interaction caused by the equatorial bond pair towards the axial bonds, the axial bond pairs are slightly longer to reduce repulsive interaction, but due to increasing its length its strength reduces ( i..e.. length of bond is inversely proportional to the strength of bond ) and so axial bonds are slightly weaker than equatorial bond due to more repulsive interaction from equatorial bond pairs.

Q – 8 Hybridization of PBr₅ and PCl₅?

  • In a gaseous state phosphorous of both PBr₅ and PCl₅ exists in sp³d hybridization.

  • But in solid state p of PCl₅ exists in both sp³d² and sp³ hybridization state, while phosphorous i..e.. p of PBr₅ will exist in sp³ hybridization only.

Q-9 What is the geometry of PCl4+?

  • In PCl4+, there is a 4 p – cl bond and no lone pair.

  • So the geometry of pcl4+ will be tetrahedral.

Read useful topics:

Summary

PCl5 has sp3d hybridization and trigonal pyramidal geometry and there is no lone pair in PCl5 so its is Trigonal Pyramidal.

NCERT Chemistry Notes :

Frequently Asked Questions (FAQs)

1. What is the hybridization of PCl5?
The hybridization of PCl5 (phosphorus pentachloride) is sp3d. This means that one s orbital, three p orbitals, and one d orbital of the phosphorus atom combine to form five equivalent hybrid orbitals, which are used to form bonds with the five chlorine atoms.
2. Why does PCl5 use sp3d hybridization instead of sp3?
PCl5 uses sp3d hybridization because phosphorus needs to accommodate five bonding pairs around it. The sp3 hybridization only provides four hybrid orbitals, which is insufficient for PCl5. By including a d orbital in the hybridization, phosphorus can form the required five bonds.
3. What is the Lewis structure of PCl5?
The Lewis structure of PCl5 shows a central phosphorus atom bonded to five chlorine atoms. There are five single bonds between P and Cl, and no lone pairs on the phosphorus. Each chlorine atom has three lone pairs.
4. How many valence electrons does phosphorus have in PCl5?
In PCl5, phosphorus has 5 valence electrons. Phosphorus is in group 15 of the periodic table, so it naturally has 5 valence electrons. In PCl5, it uses all of these to form bonds with the chlorine atoms.
5. What is the molecular geometry of PCl5?
The molecular geometry of PCl5 is trigonal bipyramidal. This means that three chlorine atoms are arranged in a triangular shape in one plane (equatorial positions), while the other two chlorine atoms are positioned above and below this plane (axial positions).
6. What is the oxidation state of phosphorus in PCl5?
The oxidation state of phosphorus in PCl5 is +5. This is because each chlorine atom (being more electronegative) is assigned a -1 oxidation state, and the molecule is neutral overall, so phosphorus must have a +5 oxidation state to balance.
7. How does PCl5 react with water?
PCl5 reacts vigorously with water in a hydrolysis reaction. The products are phosphoric acid (H3PO4) and hydrochloric acid (HCl). The reaction can be represented as: PCl5 + 4H2O → H3PO4 + 5HCl
8. What is the significance of PCl5 in organic synthesis?
PCl5 is significant in organic synthesis as a chlorinating agent. It can convert alcohols to alkyl chlorides, carboxylic acids to acyl chlorides, and can also be used to replace oxygen with chlorine in various organic compounds.
9. Why doesn't PCl5 follow the octet rule?
PCl5 doesn't follow the octet rule because phosphorus has more than 8 electrons in its valence shell. This is possible because phosphorus, being a third-period element, has access to d orbitals which can be used in bonding, allowing it to expand its octet.
10. What is the bond angle between the equatorial chlorine atoms in PCl5?
The bond angle between the equatorial chlorine atoms in PCl5 is 120°. This is because the three equatorial chlorines are arranged in a triangular shape in the same plane, with equal angles between them.
11. What is the bond angle between an axial and an equatorial chlorine in PCl5?
The bond angle between an axial and an equatorial chlorine in PCl5 is 90°. This is because the axial chlorines are perpendicular to the plane of the equatorial chlorines in the trigonal bipyramidal structure.
12. Are all P-Cl bonds in PCl5 equivalent?
No, not all P-Cl bonds in PCl5 are equivalent. The axial bonds are slightly longer and weaker than the equatorial bonds due to greater repulsion between the axial chlorine atoms.
13. Why is PCl5 polar despite its symmetrical structure?
PCl5 is actually non-polar despite its seemingly asymmetrical structure. The trigonal bipyramidal arrangement of the chlorine atoms around the phosphorus results in a symmetrical distribution of charge, canceling out any individual bond dipoles.
14. Why is PCl5 considered a Lewis acid?
PCl5 is considered a Lewis acid because it can accept an electron pair to form an adduct. The phosphorus atom in PCl5 can expand its octet to form a sixth bond, making it capable of accepting an electron pair from a Lewis base.
15. What is the shape of the hybrid orbitals in PCl5?
The hybrid orbitals in PCl5 have a trigonal bipyramidal shape. Three of the sp3d hybrid orbitals are oriented in a triangular arrangement in one plane, while the other two are positioned perpendicular to this plane, above and below it.
16. How does the VSEPR theory explain the structure of PCl5?
VSEPR (Valence Shell Electron Pair Repulsion) theory explains that the five electron pairs around the phosphorus in PCl5 arrange themselves to minimize repulsion. This results in the trigonal bipyramidal geometry, where the electron pairs are as far apart as possible.
17. Can PCl5 form a coordinate covalent bond?
Yes, PCl5 can form a coordinate covalent bond by acting as a Lewis acid. It can accept an electron pair from a Lewis base to form a complex ion, such as [PCl6]-, where the sixth chloride ion donates a lone pair to the phosphorus.
18. What is the difference between the structure of PCl5 in solid state and gas phase?
In the gas phase, PCl5 exists as discrete trigonal bipyramidal molecules. However, in the solid state, it exists as an ionic compound consisting of [PCl4]+ cations and [PCl6]- anions, due to autoionization.
19. How does the hybridization of PCl5 compare to that of PF5?
The hybridization of PCl5 and PF5 is the same: both use sp3d hybridization. This is because both molecules have a central phosphorus atom bonded to five halogen atoms, resulting in the same trigonal bipyramidal geometry.
20. Why is PCl5 unstable at room temperature?
PCl5 is unstable at room temperature because it readily dissociates into PCl3 and Cl2. This is due to the weakness of the axial P-Cl bonds and the stability of the PCl3 molecule, which follows the octet rule.
21. How does the electronegativity difference between P and Cl affect the bonding in PCl5?
The electronegativity difference between P and Cl makes the P-Cl bonds polar, with chlorine being more electronegative. This polarity contributes to the reactivity of PCl5, particularly its susceptibility to hydrolysis.
22. What is the hybridization of the chlorine atoms in PCl5?
The chlorine atoms in PCl5 are not hybridized. They use their unhybridized p orbitals to form sigma bonds with the sp3d hybrid orbitals of phosphorus. Each chlorine atom also has three lone pairs in its other p orbitals.
23. How does the structure of PCl5 relate to its reactivity?
The structure of PCl5, with its expanded octet and polar P-Cl bonds, contributes to its high reactivity. The trigonal bipyramidal geometry results in weaker axial bonds, making PCl5 prone to dissociation and nucleophilic attack.
24. What is the formal charge on the phosphorus atom in PCl5?
The formal charge on the phosphorus atom in PCl5 is 0. This can be calculated as: [# of valence electrons (5)] - [# of non-bonding electrons (0)] - [1/2 * # of bonding electrons (10)] = 5 - 0 - 5 = 0.
25. How does PCl5 demonstrate the concept of hypervalency?
PCl5 demonstrates hypervalency because the central phosphorus atom has more than eight electrons in its valence shell. This is possible due to the involvement of d orbitals in bonding, allowing phosphorus to expand its octet and form five bonds.
26. What type of isomerism is possible in PCl5?
PCl5 can exhibit geometric isomerism in its reactions. For example, when it forms complexes like [PCl5F]-, there can be isomers where the F- ion is in either an axial or equatorial position relative to the trigonal bipyramidal PCl5 structure.
27. How does the bond order in PCl5 compare to that in PCl3?
The P-Cl bond order in PCl5 is lower than in PCl3. In PCl5, the five bonds share the electron density from phosphorus, resulting in weaker individual bonds. In PCl3, there are only three bonds sharing the electron density, making them stronger.
28. What is the relationship between the structure of PCl5 and its dipole moment?
Despite having polar P-Cl bonds, PCl5 has a net dipole moment of zero. This is because the trigonal bipyramidal structure results in a symmetrical distribution of charge, with the individual bond dipoles canceling each other out.
29. How does the atomic radius of phosphorus affect its ability to form PCl5?
The larger atomic radius of phosphorus, compared to elements in the second period, allows it to accommodate five chlorine atoms around it. This larger size, along with the availability of d orbitals, enables phosphorus to expand its octet and form PCl5.
30. What role do the d orbitals play in the bonding of PCl5?
In PCl5, one d orbital of phosphorus participates in sp3d hybridization. This d orbital combines with one s and three p orbitals to form five equivalent hybrid orbitals, allowing phosphorus to form five bonds and expand its octet.
31. How does the electron domain geometry of PCl5 differ from its molecular geometry?
In PCl5, the electron domain geometry and molecular geometry are the same: trigonal bipyramidal. This is because all electron domains around phosphorus are bonding pairs, with no lone pairs. Therefore, the arrangement of atoms (molecular geometry) directly reflects the arrangement of electron domains.
32. What is the bond angle between the two axial chlorine atoms in PCl5?
The bond angle between the two axial chlorine atoms in PCl5 is 180°. This is because they are positioned directly opposite each other, above and below the plane of the equatorial chlorine atoms in the trigonal bipyramidal structure.
33. How does the presence of d orbitals in phosphorus affect its ability to form PCl5?
The presence of accessible d orbitals in phosphorus allows it to undergo sp3d hybridization. This hybridization produces five equivalent orbitals, enabling phosphorus to form five bonds and expand its octet, which is necessary for the formation of PCl5.
34. How does the structure of PCl5 influence its melting and boiling points?
The structure of PCl5 influences its melting and boiling points through intermolecular forces. Despite being a polar molecule, PCl5 has relatively low melting and boiling points due to weak van der Waals forces between molecules, a result of its symmetrical charge distribution.
35. What is the hybridization of the phosphorus atom in the [PCl6]- ion?
In the [PCl6]- ion, the phosphorus atom undergoes sp3d2 hybridization. This allows it to form six equivalent bonds with the chlorine atoms, resulting in an octahedral geometry.
36. How does the concept of atomic orbital overlap apply to the formation of PCl5?
In PCl5, the sp3d hybrid orbitals of phosphorus overlap with the p orbitals of chlorine to form sigma bonds. The overlap occurs end-on, resulting in strong covalent bonds between phosphorus and chlorine atoms.
37. What is the relationship between the structure of PCl5 and its ability to act as a Lewis acid?
The trigonal bipyramidal structure of PCl5, resulting from sp3d hybridization, leaves room for the phosphorus atom to accept another electron pair. This ability to expand its coordination number makes PCl5 a good Lewis acid, capable of forming adducts with Lewis bases.
38. How does the electronegativity of chlorine affect the stability of PCl5?
The high electronegativity of chlorine makes the P-Cl bonds polar, with a partial negative charge on chlorine. This polarity contributes to the reactivity of PCl5, making it susceptible to nucleophilic attack and hydrolysis, which affects its stability.
39. What is the significance of the axial and equatorial positions in PCl5?
The axial and equatorial positions in PCl5 are significant because they are not equivalent. The axial bonds are slightly longer and weaker than the equatorial bonds due to greater repulsion. This difference affects the reactivity and properties of PCl5.
40. How does the concept of molecular orbital theory apply to PCl5?
Molecular orbital theory describes the bonding in PCl5 as a combination of atomic orbitals to form molecular orbitals. The sp3d hybrid orbitals of phosphorus combine with p orbitals of chlorine to form bonding and antibonding molecular orbitals, determining the overall stability of the molecule.
41. What is the relationship between the structure of PCl5 and its vapor pressure?
The structure of PCl5, with its symmetrical charge distribution, results in weak intermolecular forces. This leads to a relatively high vapor pressure, as less energy is required to overcome these forces and convert the substance from liquid to gas.
42. How does the concept of resonance apply to PCl5?
Resonance does not significantly apply to PCl5 in its ground state. The molecule is best described by a single Lewis structure with five single bonds. However, in reactions or excited states, resonance structures involving multiple bonds might be considered.
43. What is the significance of the 90° and 120° bond angles in PCl5?
The 90° and 120° bond angles in PCl5 are a result of its trigonal bipyramidal geometry. The 120° angles between equatorial chlorines minimize repulsion in the equatorial plane, while the 90° angles between axial and equatorial chlorines allow for the most efficient packing of five atoms around the central phosphorus.
44. How does the structure of PCl5 relate to its reactivity in substitution reactions?
The trigonal bipyramidal structure of PCl5 makes it prone to substitution reactions, particularly at the axial positions. The axial bonds are longer and weaker, making them more susceptible to nucleophilic attack. This structural feature contributes to PCl5's usefulness as a chlorinating agent in organic synthesis.
45. What is the relationship between the hybridization of PCl5 and its magnetic properties?
The sp3d hybridization of PCl5 results in all electrons being paired, making the molecule diamagnetic. This means PCl5 is slightly repelled by magnetic fields, a property directly related to its electronic structure and hybridization.
46. How does the concept of electron-domain repulsion explain the geometry of PCl5?
Electron-domain repulsion theory (VSEPR) explains that the five bonding pairs of electrons in PCl5 arrange themselves to minimize repulsion. This results in the trigonal bipyramidal geometry, where the electron domains (bonds) are as far apart as possible, leading to the observed 90° and 120° bond angles.
47. What is the significance of the expanded octet in PCl5?
The expanded octet in PCl5 allows phosphorus to form five bonds, exceeding the usual octet of eight electrons. This is possible due to the availability of d orbitals in phosphorus, demonstrating that the octet rule is not universal and can be violated by elements in the third period and beyond.
48. How does the structure of PCl5 influence its solubility in polar and non-polar solvents?
Despite having polar P-Cl bonds, PCl5 is overall non-polar due to its symmetrical structure. This makes it more soluble in non-polar solvents. However, its reactivity with polar solvents like water (resulting in hydrolysis) complicates its solubility behavior in polar media.
49. What is the relationship between the structure of PCl5 and its ability to conduct electricity?
In its pure form, PCl5 does not conduct electricity as it does not have free ions or electrons. However, when dissolved in a polar solvent or melted, it can conduct electricity due to the formation of ions through

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