Hybridization: Types & Examples

Hybridization is intermixing of atomic orbitals of different energy and shapes to form new hybrid orbitals. Hybrid orbitals have the same energy and shape. Linus Pauling introduced the phenomenon of hybridization to explain molecular geometries. There are different types of hybridization depending upon the number and nature of orbitals taking part in hybridization i.e, sp, sp2, sp3, dsp2, sp3d, sp3d2, sp3d3, etc.

 

Linus Pauling explained the structure of simple molecules like CH4. According to him all C-H bonds of methane are identical. He pointed out that in methane molecules four atomic orbital carbon atom are involved in bonding. There is no pi-bond distribution in CH4 molecules. All four bonds in CH4 are sigma bonds having the same length. The concept of hybridization can also be applied to double bonds and triple bonds.

Hybridization is a concept of mixing two or more non-equivalent atomic orbitals of comparable energy and different shapes. For example, atomic orbitals are s and p subshell.

atomic orbitals of p and s subshell

When they intermix they form new orbitals called hybrid orbitals. These orbitals are of the same energy and shape.

s and p orbitals showing hybridization general mechanism

Their energy is always lower than the energy of parent orbitals. Hence hybrid orbitals are more stable as compared to the parent atomic orbitals.

Hybridization is the description of observed molecular geometry and electron density. Because of hybridization molecules adopt a particular shape to overcome repulsive interactions. It tells us how molecular geometry is affected by ligands and electrons at a particular atom. Hybrid orbitals maintain maximum separation in bonds.

Key features of the hybridization

  • Hybridization is the theoretical model to explain covalent bonding.
  • For hybridization, there must be two or more non equivalent orbitals to mix.
  • It involves unpairing and promotion of the electrons to the next available orbital. This is called the excitation of electrons.
  • Excited orbitals then undergo hybridization.
  • There is a conservation of orbitals.
  • The number of hybrid orbitals is equal to the number of atomic orbitals mixed.
  • The newly formed orbital has the same energy and shape.
  • The hybrid orbitals do not exist in free form.
  • Not only half filled orbitals undergo hybridization, but completely filled and empty orbitals can also undergo hybridization.
  • Bond formation occurs when hybrid orbitals overlap with suitable orbitals of other atoms.
  • Atomic orbitals of the same energies can undergo hybridization and form stronger bonds.

Types of hybridization:

The types of hybridization depend upon the number and kinds of atomic orbitals involved in hybridization.

When only s and p orbitals are involved then,

  • sp
  • sp2
  • sp3

When s, p, and d orbital are involved then,

  • dsp2
  • sp3d
  • sp3d2
  • sp3d3

sp Hybridization

  • When one s and one p -orbital combine together to form two hybrid orbitals of the same shape and energy it is called sp hybridization.
  • They give a linear molecule.
  • There is an angle of 1800 between two hybrid orbitals.
  • Each sp hybrid orbital has 50% s-character and 50% p-character.
  • These two hybrid orbitals lie in one plane oriented in opposite directions.

Examples of sp hybridized molecules:

Ethyne, BeH2, HgX2, BeF2, CO2, BeCl2, etc.

Hybridization of BeCl2

  • One s and one p orbital of beryllium are involved in bonding.
  • Two sigma bonds are formed between Be-Cl
  • In the ground state, Be has no unpaired electrons.
  • It has two electrons in 1s orbitals and two electrons in 2s orbitals.
  • Be atom undergoes excitation and promotes one of its 2s electrons into an empty 2p orbital
  • This results in two half-filled sp hybrid orbitals.
  • These orbitals have the same energy and shape.
  • Electron density is symmetrically distributed between these two atoms.
  • Be atom lies in the center surrounded by two oppositely directed Cl bonds.
  • BeCl2 has linear geometry.
  • There is an 1800 angle between hybrid orbitals.

BeCl2 hybridization example of sp hybridization

sp2 Hybridization

  • When one s and two p-orbitals on the same atom intermix to form three identical sp2 hybridized orbitals it is called sp2 hybridization.
  • These sp2 hybrid orbitals have the same energy and shape.
  • All the hybrids lie in one plane.
  • The bond angle between any two orbitals is 1200.
  • All the bonds are directed toward the corners of the triangular plane.
  • sp2 hybridized molecules have a trigonal planar geometry
  • In sp2 hybridization, there will be 33% s-character and 66% p-character.

Examples of sp2 hybridization

BF3, BH3, SO3, SO2, PbCl2, etc.

Hybridization of BCl3

  • Boron is the central atom bonded to three chlorine atoms.
  • In the ground state, Boron has one unpaired electron.
  • It promotes one of its 2s electrons to the empty p orbital.
  • Now it has three unpaired electrons in three half filled orbitals.
  • Now boron undergoes sp2 hybridization by using one 2s and two 2p orbitals.

BCl3 hybridization example of sp2 hybridization

sp3 Hybridization

  • It involves the mixing of one s and three p-orbitals on the same atom to form four identical sp3 hybrids.
  • All the sp3 hybrids are directed at the corners of a regular tetrahedron.
  • sp3 hybridized molecules exhibit tetrahedral geometry.
  • The bond angle between any two bonds is 109.50.
  • In sp3 hybridization, there will be 25% s-character and 75% p-character.

Examples of sp3 hybridization

H2O, PF3, PCl3, CH4, etc

Hybridization of CH4 molecule

  • In the CH4 molecule, the carbon atom undergoes sp3 hybridization.
  • The carbon atom is the central atom having two unpaired electrons in p orbitals in the ground state.
  • In the excited state one of the 2s electrons is promoted to the p orbital.
  • Now it has four half filled orbitals available for bonding.
  • By mixing one 2s and three 2p orbitals to form four sp3 hybrid orbitals.
  • All sp3 hybrid orbitals form a sigma bond(C-H sigma bond).
  • The bond angle between any two bonds is 109.5.

CH4 hybridization example of sp3 hybridization

dsp2 Hybridization

  • In this type of hybridization, the d orbital is also involved.
  • It is the mixing of one s two p and one d orbitals on the same atom to form four identical dsp2 hybrid orbitals.
  • All four hybrid orbitals are oriented to the corners of a square.
  • dsp2 hybridized molecules have square planar geometry.
  • It is mostly encountered in coordination compounds because of the d orbital.

Examples of dsp2:

[Ni(CN)4]2- 

  • Nickel is a diamagnetic molecule having valence shell electronic configuration 3d8, 4s2.
  • In Ni+2 valence shell electronic configuration is 3d8, 4s0.
  • CN is the strong field ligand it will pair up all the electrons.
  • CN donates its electron pair bonding.
  • The empty 3d, 4s, and 4p orbitals undergo dsp2 hybridization and make bonds with CN- ligands.
  • It has square planar geometry.

Ni(CN)4]2- hybridization example of dsp2 hybridization

sp3d Hybridization

  • In this type of hybridization one s, three p, and one d orbitals are involved to form five hybrid orbitals.
  • All hybrid orbitals are not equivalent.
  • All sp3d hybrids are oriented towards the corners of a trigonal bipyramid.
  • They form three coplanar bonds having a bond angle of 1200.
  • The other two bonds are at a right angle one above and the other below the plane.

Examples of sp3d:

SF4, PCl5(g), XeF2, PBr5, AsCl5, ClF3, I3, IF2, etc.

Hybridization of PCl5

  • It is a nonpolar molecule because both axial bonds cancel the dipole moment.
  • All five bonds are not equivalent.
  • The three orbitals are directed trigonally.
  • These are called equatorial orbitals.
  • These are slightly different from linearly oriented orbitals.
  • These orbitals are known as axial orbitals.

PCl5 hybridization example of sp3d

sp3d2 Hybridization

  • In this type of hybridization one s, three p, and two d atomic orbitals are involved in the hybridization.
  • They give six equivalent hybrid orbitals.
  • These orbitals are oriented toward the corner of the octahedron.
  • The bond angle between any two bonds is 900.

Examples of sp3d2:

SF6, IF5, XeF4, PBr5, AsCl5 etc.

Hybridization of SF6

  • Sulfur is the central atom having two unpaired electrons in a 3p orbital.
  • In order to bond with six fluorine atoms, it requires six half filled orbitals.
  • For this purpose, it promotes one of 3s electron and one of 3 p electron to two empty d orbitals.
  • Now it has 6 unpaired electrons in an excited state.
  • These orbitals hybridized to give six sp3d2 hybrid orbitals.
  • These hybrid orbitals are directed to the corner of a regular octahedron.

SF6 hybridization example of sp3d2

sp3d3 Hybridization

  • In this type of hybridization one s, three p, and three d atomic orbitals are involved in the hybridization.
  • They give seven hybrid orbitals.
  • These orbitals are not equivalent.
  • Five of them are pointed toward the vertices of the pentagon
  • They have a bond angle of 720.
  • The remaining two are perpendicular to the plane.
  • They have a bond angle of 900.
  • These orbitals are oriented toward the corner of the pentagonal bipyramid.

Examples of sp3d3

IF7

Hybridization of IF7

  • Iodine is the central atom having one unpaired electron in a 5p orbital.
  • In order to bond with seven fluorine atoms, it requires seven half filled orbitals.
  • For this purpose, it promotes one of 5s electron and two of 5p electron to three empty 5d orbitals.
  • Now it has 7 unpaired electrons in an excited state.
  • These orbitals are hybridized to give seven sp3d3 hybrid orbitals.
  • These hybrid orbitals are directed to the corner of the regular pentagon

IF7 hybrization example of sp3d3 hybrization

 

Key takeaways

HybridizationOrbital involvedGeometryBond anglesExamples
spOne s

One p

linear1800BeCl2, CO2
sp2One s

Two p

Trigonal planar1200BCl3, BF3, SnCl2, SO3
sp3One s

Three p

Tetrahedral109.50CH4, C2H6, H2O, NH3
sp2dOne s

Two p

One d

Square planar900[Ni(CN)4]2-
sp3dOne s

Three p

One d

Trigonal bipyramidal3 bonds 1200

2 bonds 900

PCl5, PBr5, AsCl5, SF4
sp3d2One sThree pTwo doctahedral900Sf6, XeF4, IF5
sp3d3One sThree pThree dPentagonal bipyramid5 bonds 7202 bonds 900IF7

Concepts Berg

Who introduced the concept of hybridization?

The concept of hybridization was proposed by L. Pauling in 1931 to explain the tetrahedral

the geometry of methane-type compounds.

What is the difference between molecular and hybrid orbitals?

Molecular orbital Hybrid orbital
Molecular orbitals are formed by mixing atomic orbitals of different atoms.Hybrid orbitals are formed by mixing of atomic orbitals in the same atom in order to make a covalent bond
They are formed between two atoms.Hybrid orbitals are formed in the same atom.
Molecular orbital gives information about

antibonding orbital.

They do not give information about antibonding orbitals.

What is meant by molecular geometry?

Molecular geometry is the three dimensional arrangement of atoms in a molecule. It can be determined by the central atoms, ligands, and electron pairs.

What are degenerate orbitals?

Atomic orbitals having the same energy levels are called degenerate orbitals. An atom has s,p,d, and f subshell. The p orbital has three degenerate orbitals px, py, and pz.

What are hybrid orbitals?

It is an orbital formed by the mixing of two or more atomic orbitals of different energy and shape.

Differentiate between hybrid and degenerate orbitals?

Hybrid orbitalDegenerate orbital
Hybrid orbitals are formed by the mixing of two or more atomic orbitals.Degenerate orbitals are atomic orbitals having the same energy.
Formed by mixing two or more atomic orbitals.These orbitals already exist in an atom.
They have the same energy.These are atomic orbitals having the same energy.
sp, sp2, and sp3 are hybrid orbitals.px, py, pz orbitals in the p subshell are degenerate orbitals.

What is the difference between VSEPR and VBT?

Valence shell electron pair repulsion theoryValence bond theory
It is used to predict the geometry of molecules.It is used to explain chemical bonding in covalent compounds.
It is based on the electrostatic repulsion between the lone pairs and electron pairs.It is based on the overlapping of orbitals for the formation of covalent bond.
It does not give details of orbital that are present in atoms of a molecule.It gives details of orbitals present in atoms of a molecule.
It does not predict the type of bonds present between atoms.The type of bond present between atoms can be predicted on basis of VBT.

Does VBT explain the resonance structure of molecules?

Yes, VBT can explain the resonance structure of molecules. it can represent the full electronic structure of molecules.

What are the drawbacks of VBT?

  1. This theory is unable to explain the difference between square planar and tetrahedral geometry.
  2. It is unable to explain the paramagnetic behavior of O2.
  3. VBT cannot explain the non-existence of noble gas molecules.
  4. It is unable to explain the structures of odd electron molecules or ions where no pairing of electrons occurs.

References

  • Second edition of Inorganic Chemistry by Catherine E. Housecroft and Alan G. Sharpe
  • Caravan Advanced Inorganic Chemistry by Haq Nawaz Bhatti.
  • Tenth edition of Chemistry by Raymond Chang.
  • Orbital hybridisation by (en.wikipedia.org)

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