1. Valence Bond Theory was developed in the year?
a) 1916
b) 1927
c) 1930
d) 1932
Explanation: The Valence Bond Theory was developed in 1927 by Heitler and London.
2. According to VBT, the formation of a stable bond requires _____________
a) The electrons should have opposite spins
b) The two atoms should be close to each other
c) The greater overlapping of the electron clouds
d) All of the mentioned
Explanation: According to VBT, when two atoms come closer to each other with opposite electron spins, due to mutual rearrangements (or overlapping) of their electron clouds, energy changes are produced.
3. The s-orbital does not show preference to any direction because _____________
a) It is the smallest orbital
b) It is present in every atom
c) It is spherically symmetric
d) It is the first orbital
Explanation: The s-orbital is spherically symmetric in shape so it does not show preference to any direction. It is the same from all the directions.
4. The p-orbital is in the shape of a _____________
a) Sphere
b) Dumbbell
c) Pear-shaped lobe
d) None of the mentioned
Explanation: The p-orbital is in the shape of a Dumbbell. It has 2 lobes that are pointing in opposite directions.
5. The Valence Bond Theory does not explain the paramagnetic nature of oxygen molecule.
a) True
b) False
Explanation: Oxygen molecule is paramagnetic in nature, although it does not contain unpaired electrons which is not explained in VBT.
6. According to VBT, the direction of a bond which is formed due to overlapping will be _____________
a) In the same direction in which orbitals are concentrated
b) In the opposite direction in which orbitals are concentrated
c) Perpendicular to the direction in which orbitals are concentrated
d) None of the mentioned
Explanation: The direction of the bond formed will be in that direction in which the orbitals are concentrated. For Example: When two px orbitals overlap, the bond is formed along the x-axis.
7. Which orbital would form a more stronger bond if both of them have identical stability?
a) The one which is less directionally concentrated
b) The one which is more directionally concentrated
c) Both will be equally strong
d) It differs from atom to atom
Explanation: When the two orbitals have identical stability or energy, the one which is more directionally concentrated would form a stronger bond.
8. The formation of odd electron molecules such as H2+, NO, O3 is also explained in VBT.
a) True
b) False
Explanation: The Valence Bond Theory does not explain the formation of odd electron molecules such as H2+, NO, O3 etc, where no electron pairing takes place.
9. Hybridisation of Acetylene is _____________
a) sp
b) sp2
c) sp3
d) dsp2
Explanation: The Acetylene molecule is C2H2. It is sp hybridised.
10. Shape of PCl5 molecule is _____________
a) Tigonal Planar
b) Linear
c) Trigonal bipyramidal
d) Tetrahedral
Explanation: PCl5 is trigonal bipyramidal with its bond angle equal to 1200 and 900.