2. CHEMICAL BOND
1. Explain how covalent bond is formed?
A. Sharing of electrons lead to the formation of
Covalent bond. (OR)
The formed by sharing of electrons between two
atoms is called Covalent bond. (OR)
Covalent bond is formed by sharing of electrons
between atoms.
2. Draw the bond formation of in HCl molecule?
A. Formation of HCl molecule by s-p overlap:
1s of Hydrogen atom
2pz of Chlorine atom
s-p overlap in H-Cl
HCl molecule
3. Show the electron dot picture of H2 molecule?
A. The bond formation in H2 molecule is represented
by electron dot method as follows.
4. What is the shape of Ammonia molecule?
A. Ammonia molecule ( NH3 ) has a pyramidal
shape. The three hydrogens are in one plane
and nitrogen above the plane. Nitrogen has one
lone pair of electrons in ammonia.
5. Give three examples of molecules having a
double bond?
A. Molecules having a double bond :
Oxygen(O2) ,Ethylene(C2H4) ,Carbon dioxide (CO2).
6. Give three examples of molecules having a
triple bond?
A. Molecules having a triple bond :
Nitrogen (N2) , Acetylene (C2H2) ,
7. Name two molecules having Pyramidal shape?
A. Molecules having Pyramidal shape:
Ammonia (NH3), Phosphorous tri chloride (PCl3) ,
Phosphene (PH3) .
8. What is the shape of PCl5 molecule?Draw it.
A. Phosphorous penta chloride ( PCl5 )
has a Trigonal bipyramidal shape. The three
chlorines and phosphorous lie in one plane and
one chlorine above the plane and one chlorine
below the plane.
9. Name two molecules having p-p overlap.
A. Molecules having p-p overlap :
Fluorine(F2) ,Chlorine(Cl2) ,Bromine(Br2) ,Iodine(I2)
10. Which orbitals can form π bond ?
A. p and d orbitals can form π bond.
11. What is the shape of Carbon dioxide?
A. Shape of Carbon dioxide is linear.
12. What is the shape of Water molecule?Draw it.
A. Water molecule(H2O) is non-linear and has a ‘V’
shape. Oxygen has two lone pairs of
electrons in Water molecule.
13. Distinguish between Sigma and Pi bonds?
Sigma bond
Pi bond
1.The bond formed by
1.The bond formed by
the end-on-end
the side-on overlap of
overlap of orbitals of
orbitals of atoms is
atoms is called sigma
called Pi bond.
bond.
2.It exist independently.
2.It can not exist
independently.
3.It is a strong bond.
3.It is a weak bond.
4.In this bond maximum 4.The extent of overlap is
overlap takes place.
much less than in
sigma bond.
5.Orbitals overlap along
5.Orbitals not overlap
their axes.
along their axes.
14. Define Ionic bond (or) electrovalent bond?
Give examples.
A. Complete transfer of one or more electrons from
one atom to another will lead to the formation of
ionic bond. (OR)
The chemical bond by transfer of electrons from
one atom to another atom is called ionic bond.
15. What is the shape of Phosphorous
trichloride? Draw it.
A. Phosphorous trichloride (PCl3)
P
molecule has a pyramidal shape.
The three chlorines are in
one plane and Phosphorous
above the plane. Phosphorous Cl
Cl
Cl
has one lone pair of electrons in PCl3.
16. Discuss the types of overlaps that are
possible with s and p orbitals?
A. Three types of overlaps are possible with s and p
orbitals. They are
(i) s-s overlap
(ii) s-p overlap (iii) p-p overlap
(i) s-s overlap: The s orbitals in two atoms which
are having one unpaired electrons approach
each other. The overlap between s orbitals of
two atoms is known as s-s overlap.
Ex: H2
The s orbitals in two Hydrogen atoms gets overlap
(ii) s-p overlap: The s orbital of one atom and p
orbital in another atom which are having one
unpaired electrons approach each other. The
overlap between s orbital of one atom and p
orbital in another atom is known as s-p overlap.
Ex: HCl
The s orbital of Hydrogen atom and p orbital of
Chlorine atoms gets overlap.
(iii) p-p overlap: The p orbitals in two atoms which
are having one unpaired electrons approach
each other. The overlap between p orbitals of
two atoms is known as p-p overlap.
Ex: Cl2
The p orbitals in two Chlorine atoms gets overlap.
Formation of Triple bond in Nitrogen molecule
19.Explain how sigma and Pi bonds are formed?
A. Sigma bond: The bond formed by the end-onend overlap of orbitals of atoms is called sigma
bond. It can exist independently. It is a strong
bond. In this bond maximum overlap takes place.
Orbitals overlap along their axes. s,p,d,.. orbitals
can participate in this bond.
σ s-s overlap
17. Explain the formation of a double bond?
A. Double bond: If two electron pairs are shared
between two atoms, the bond formed is called a
tdouble bond.
Ex: Oxygen(O2)
Explanation: Electronic configuration of
Oxygen (Z=8) is 1s22s22p4.
1s 2s 2px 2py 2pz
It has unpaired electrons in 2py, 2pz orbitals.
The 2pz orbitals which are having unpaired
electrons in two Oxygen atoms overlap end-onend to give rise to sigma bond.
Next the 2py orbitals in two Oxygen atoms
overlap sideways giving rise to one Pi bond.
Thus in Oxygen molecule there are one
σ bond and one π bond.So it is called double bond.
Formation of Double bond in Oxygen molecule
18. Explain the formation of a triple bond?
A. Triple bond: If three electron pairs are shared
between two atoms, the bond formed is called a
triple bond.
Ex: Nitrogen(N2)
Explanation: Electronic configuration of
Nitrogen(Z=7) is 1s22s22p3.
1s 2s 2px 2py 2pz
It has unpaired electrons in 2px, 2py, 2pz orbitals.
The 2pz orbitals which are having unpaired
electrons in two nitrogen atoms overlap end-onend to give rise to sigma bond.
Next the 2px and 2py orbitals in two nitrogen
atoms overlap sideways giving rise to two Pi bonds.
Thus in Nitrogen molecule there are one
σ bond and two π bonds. So it is called triple bond.
σ s-p overlap
σ p-p overlap
Pi bond: The bond formed by the side-on overlap
of orbitals of atoms is called Pi bond. It can not
exist independently. It is a weak bond. In this bond
the extent of overlap is much less than in sigma
bond. Orbitals not overlap along their axes. p,d,..
orbitals can participate in this bond.
20. Explain the formation of Co-ordinate covalent
bond ?
A. coordinate covalent bond: one atom contributes
two electrons( one lone pair of electrons) and the
other atom contributes no electrons in the
formation of a bond. The electrons are shared by
the atoms. This type of bond is called coordinate
covalent bond.
The atom which give the pair of electrons is
called as donar and the other is called acceptor.
This bond is designated as  . the arrow direction
indicates the donar and the acceptor of the electron
pair. In the bond formation.
Ex: NH3BF3 , NH4+ , H3O+
Explanation: coordinate covalent bond exist in
Ammonia Boron Tri fluoride(NH3BF3). Ammonia
molecule has pyramidal shape and has one lone
pair of electrons on Nitrogen. Boron tri fluoride has
planar triangular shape and has one empty p orbital
in Boron. NH3 molecule donate the pair of electrons
to BF3.
H N : + BF  H N : BF (OR) (H NBF )
3
3
3
3
3
3
Formation of NH3BF3
21. Draw the diagram showing the formation of a
double bond?
A.
Diagram in the answer of 17th Question
22. Draw the diagram showing the formation of a
triple bond?
A. Diagram in the answer of 18th Question
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