Daily Practice Problems
Overall
Score Total no of Correct Incorrect Unattempted
question
15 10 4 1 5
Solution
1 Which of the following statements is correct 0s
regarding the Valence Bond theory?
Covalent bonds are formed when two valence
A
orbitals (half-filled) belonging to two different
atoms overlap with each other
BThe unpaired electrons in the valence shell
participate in the formation of a chemical bond
C Formation of a covalent bond leads to the
stability of molecule
D All of the above
Solution : D
Valence Bond Theory illustrates that two
half-filled valence orbitals of two different
atoms overlap and produce a chemical
bond between two atoms. The unpaired
electrons are shared and a covalent bond
is formed.
Formation of a covalent bond leads to the
stability of molecule.
4.0/4.0
2 Which one of the following molecules is formed by 1m
p − p overlapping? 13 s
A Br2
B H Br
C H2 O
D P H3
Solution : A
2 mins
a): Electronic Configuration of Br: [Ar]3d 4s 4p . 10 2 5
Bromine shows valency of 1 as the p-orbital is only
1 electron short to attain the inert gas configurtion.
So, for bonding p − p orbitals overlap occurs.
b): Electronic Configuration of H : 1s (1 valence
1
electron) and
Electronic Configuration of Br: [Ar]3d 4s 4p . 10 2 5
So, s − p orbitals overlap.
c): Electronic Configuration of H : 1s and 1
Electronic Configuration of O : 1s 2s 2p .
2 2 4
So, s − p orbitals overlap.
d): Electronic Configuration of P : 1s 2s
2 2 6
2p 3s 3p
2 3
and Electronic Configuration of H : 1s . 1
So, s − p orbitals overlap.
4.0/4.0
3 If the internuclear axis of a diatomic molecule is z, 2m
orbitals p of one atom and p of the other overlap
z y
10 s
with each other to form which of the following
bonds?
A π bond
B σ bond
C δ bond
D No bond will be formed
Solution : D
Overlapping of two perpendicular orbitals
isn't possible.
As p , p , p are perpendicular to each
x y z
other, no bond will be formed by p and p
z y
overlap as there is zero overlap between
the two.
-1.0/4.0
4 Which of the following leads to bonding? 11 s
Solution : B
2 mins
Orbitals forming a bond should have the same
sign (phase) and orientation in space.
Also, the orbitals should have the same or nearly
the same energy and the same symmetry around
the molecular axis for proper orbital overlapping
to take place. Hence, only s and p (considering z-
z
axis as internuclear axis) will lead to formation of σ
bond.
5 Choose the wrong statement according to the 2m
valence bond theory: 10 s
A A σ-bond is stronger than a π-bond
B p-orbitals always have only sideways
overlapping
C s-orbitals never form π-bonds
D There can be only one sigma bond between
two atoms
Solution : B
2 mins
(a) σbond is stronger than π bond, because
overlapping of atomic orbitals can take place to a
greater extent during the formation of sigma bond
compared to the formation of a π bond.
(b) p-orbitals can form s − p, p − p overlapping
axially also. Such bonds are called σ bonds. π
bond is formed by sideways overlapping of p -
orbitals.
(c)Only p and d-orbitals can form π bonds. s -
orbitals always form sigma bonds.
(d)When the orbitals of an atoms undergoes
head on overlapping to form a σ bond, sharing of
only two electrons are possible. For more
electrons to be shared, lateral orbital overlapping
takes place. So, there can be only one σ bond
between two atoms.
4.0/4.0
6 In C 4−
, the number of σ and π bonds are: 12 s
3
A 2 σ and 2 π bonds
B 3 σ and 1 π bonds
C 2 σ and 1 π bonds
D 2 σ and 3 π bonds
Solution : A
1 mins
Single bond contains 1 σ bond.
Triple bond contains 1 σ bond and 2 π bonds.
So the carbide ion contains a total of 2 σ bonds
and 2 π bonds.
7 Which of the following overlaps gives a σ bond with 26 s
x as the internuclear axis?
A pz and p z
B s and p z
C s and p x
D dx2 −y 2 and d z
2
Solution : C
1 mins
Sigma bond is formed by the overlap of s-s orbital
and head on overlap of s-p and p-p orbital,
4.0/4.0
8 Assuming z-axis to be the inter-nuclear axis, which 11 s
of the following overlaps is incorrect?
A 2py + 2py → π2py
B 2pz + 2pz → σ2pz
C 2px + 2px → π2px
D 1s + 2py → π(1s − 2py )
Solution : D
2 mins
2py orbitals of an atom overlaps side by side with
2p orbital of another atom and forms a π bond.
y
2p orbitals of an atom overlaps head on with 2p
z z
orbital of another atom and forms a σ bond.
2p orbitals of an atom overlaps side by side with
x
2p orbital of another atom and forms a π bond.
x
1s orbital and 2p orbital will never form π bond
y
since s orbital overlapping always forms a sigma
bond.
9 Which of the following statements is correct about 12 s
S atom in SO ?
2
A It contains two σ bonds, two π bonds and no
lone pair of electrons
B It contains two σ bonds and one π bond
C It contains two σ bonds, two π bonds and one
lone pair of electrons
D None of these
Solution : C
S atom in SO has two σ bonds,
2
two π bonds and a lone pair of electrons.
10 The strength of sigma bonds formed by the axial 4s
overlap of s - or p - orbitals of 2 shell of the
nd
participating atoms decreases as:
A s − s > p − s > p − p
B s − s > p − p > s − p
C p − s > s − s > p − p
D p − p > s − p > s − s
Solution : D
More the extent of overlap, more is the
strength of bonds. p-orbitals have more
axial overlap than s-orbitals. Directional
property of p-orbital is dominating here,
more the directional nature more the
strength of sigma bond. Hence, the order
is p − p > s − p > s − s.
