Hybridization made easy ; sp, sp², sp³ , sp³d, sp³d², sp³d³ Explained
with logic +15 solved college exam level questions
CHEAT SHEET FOR QUICK REVISION :
Steric Number (SN) = (Number of sigma bonds) + (Number of lone pairs on central
atom)
Steric Orbital Hybridization Shape Bond angle Example
number (SN)
SN= 2 One s + one sp Linear 180o C2H2
p Acetylene
SN= 3 One s + two sp2 Trigonal 120o C2H4
p planar Ethylene
SN= 4 One s + sp3 Tetrahedral 109.5o CH4
three p Methane
SN= 5 One s + sp3 d Trigonal 90o , 120o PCl5
three p + bipyramidal
one d
SN= 6 One s + sp3 d2 Octahedral 90o SF6
three p +
two d
SN= 7 One s + sp3d3 Pentagonal 72o , 90o IF7
three p + bipyramidal
three d
To understand hybridization one need to understand what is an orbital ,
These are houses of electrons in each house two electrons live i.e in each orbital two
electrons can be present but always in opposite spin - one spin up ↑, one spin down ↓.
Subshells contain fix number of orbitals :
- s subshell→ 1 orbital → holds 2 electrons
- P subshell → 3 orbitals → holds 6 electrons
- d subshell → 5 orbitals → holds 10 electrons
- f subshell → 7 orbitals → holds 14 electrons
Why hybridization is needed?
- To explain geometrical shapes of polyatomic molecules like CH₄, NH₃, H₂O.
, - Example: CH₄ is tetrahedral with 109.5° angles — but pure s and p orbitals would
predict 90°.
- The observed shapes do not match pure atomic orbitals. Something must be
happening.
Then pauling introduced this concept of hybridization according to this concept :
- Atomic orbitals combine to form new orbitals
- These new orbitals are used in bond formation.
Salient features :
- The type of hybridization indicates the geometry of the molecule.
- Hybridised orbitals are equivalent in energy and shape.
- Hybrid orbitals are more effective in bond formation than pure atomic orbitals.
Important conditions for hybridization :
- Orbitals in valence shell should be hybridised .
- Orbitals undergoing hybridization should have almost equal energy.
- Promotion of electrons is not essential prior to hybridization.
- It is not necessary that only half-filled orbitals can hybridise — even filled orbitals of
the valence shell can sometimes take part.
But will you have to see hybridization by drawing structures everytime ?
Answer is NO , see the the cheat sheet given at the top there is something written as steric
number and that is your key for exams .
Steric number (SN) =( number of sigma bonds )+ (number of lone pairs on central atom )
If SN = 2 then hybridization will be sp
If SN= 3 then hybridization will be sp 2
If SN = 4 then hybridization will be sp3
If SN = 5 then hybridization will be sp 3 d
If SN =6 then hybridization will be sp 3 d2
with logic +15 solved college exam level questions
CHEAT SHEET FOR QUICK REVISION :
Steric Number (SN) = (Number of sigma bonds) + (Number of lone pairs on central
atom)
Steric Orbital Hybridization Shape Bond angle Example
number (SN)
SN= 2 One s + one sp Linear 180o C2H2
p Acetylene
SN= 3 One s + two sp2 Trigonal 120o C2H4
p planar Ethylene
SN= 4 One s + sp3 Tetrahedral 109.5o CH4
three p Methane
SN= 5 One s + sp3 d Trigonal 90o , 120o PCl5
three p + bipyramidal
one d
SN= 6 One s + sp3 d2 Octahedral 90o SF6
three p +
two d
SN= 7 One s + sp3d3 Pentagonal 72o , 90o IF7
three p + bipyramidal
three d
To understand hybridization one need to understand what is an orbital ,
These are houses of electrons in each house two electrons live i.e in each orbital two
electrons can be present but always in opposite spin - one spin up ↑, one spin down ↓.
Subshells contain fix number of orbitals :
- s subshell→ 1 orbital → holds 2 electrons
- P subshell → 3 orbitals → holds 6 electrons
- d subshell → 5 orbitals → holds 10 electrons
- f subshell → 7 orbitals → holds 14 electrons
Why hybridization is needed?
- To explain geometrical shapes of polyatomic molecules like CH₄, NH₃, H₂O.
, - Example: CH₄ is tetrahedral with 109.5° angles — but pure s and p orbitals would
predict 90°.
- The observed shapes do not match pure atomic orbitals. Something must be
happening.
Then pauling introduced this concept of hybridization according to this concept :
- Atomic orbitals combine to form new orbitals
- These new orbitals are used in bond formation.
Salient features :
- The type of hybridization indicates the geometry of the molecule.
- Hybridised orbitals are equivalent in energy and shape.
- Hybrid orbitals are more effective in bond formation than pure atomic orbitals.
Important conditions for hybridization :
- Orbitals in valence shell should be hybridised .
- Orbitals undergoing hybridization should have almost equal energy.
- Promotion of electrons is not essential prior to hybridization.
- It is not necessary that only half-filled orbitals can hybridise — even filled orbitals of
the valence shell can sometimes take part.
But will you have to see hybridization by drawing structures everytime ?
Answer is NO , see the the cheat sheet given at the top there is something written as steric
number and that is your key for exams .
Steric number (SN) =( number of sigma bonds )+ (number of lone pairs on central atom )
If SN = 2 then hybridization will be sp
If SN= 3 then hybridization will be sp 2
If SN = 4 then hybridization will be sp3
If SN = 5 then hybridization will be sp 3 d
If SN =6 then hybridization will be sp 3 d2
