Molecular Orbital Theory MCQs
1. What is the primary concept of Molecular Orbital Theory?
a) Electrons are in fixed orbits around the nucleus
b) Electrons occupy orbitals that are a combination of atomic orbitals
c) Electrons are randomly distributed in a cloud
d) Electrons are fixed in energy levels
Answer: b) Electrons occupy orbitals that are a combination of atomic orbitals
2. What type of bond is formed by the overlap of atomic orbitals where the electron density is concentrated between the nuclei?
a) Sigma bond
b) Pi bond
c) Delta bond
d) Ionic bond
Answer: a) Sigma bond
3. In Molecular Orbital Theory, what is the result of combining two atomic orbitals?
a) Two atomic orbitals
b) One molecular orbital
c) Two molecular orbitals
d) Three molecular orbitals
Answer: c) Two molecular orbitals
4. Which type of molecular orbital has a lower energy and is formed from the constructive interference of atomic orbitals?
a) Anti-bonding molecular orbital
b) Bonding molecular orbital
c) Non-bonding molecular orbital
d) Core molecular orbital
Answer: b) Bonding molecular orbital
5. Which molecular orbital is higher in energy than the corresponding atomic orbitals?
a) Bonding molecular orbital
b) Anti-bonding molecular orbital
c) Non-bonding molecular orbital
d) Sigma molecular orbital
Answer: b) Anti-bonding molecular orbital
6. What is the bond order of a molecule?
a) The number of bonds between two atoms
b) The difference between the number of bonding and anti-bonding electrons divided by two
c) The number of electrons in the anti-bonding orbitals
d) The number of unpaired electrons in the molecule
Answer: b) The difference between the number of bonding and anti-bonding electrons divided by two
7. Which molecular orbital theory principle states that electrons will occupy the lowest energy molecular orbitals first?
a) Pauli Exclusion Principle
b) Aufbau Principle
c) Hund’s Rule
d) Heisenberg Uncertainty Principle
Answer: b) Aufbau Principle
8. In the context of Molecular Orbital Theory, what determines the magnetic properties of a molecule?
a) Bonding orbitals
b) Anti-bonding orbitals
c) The presence of unpaired electrons
d) The number of atomic orbitals involved
Answer: c) The presence of unpaired electrons
9. What is the shape of a sigma bond in a diatomic molecule?
a) Dumbbell
b) Spherical
c) Two lobes oriented along the bond axis
d) Four lobes in a planar arrangement
Answer: c) Two lobes oriented along the bond axis
10. Which of the following molecules would be diamagnetic according to Molecular Orbital Theory?
a) O₂
b) N₂
c) CO
d) NO
Answer: b) N₂
11. In Molecular Orbital Theory, how are the atomic orbitals of different atoms combined to form molecular orbitals?
a) Randomly
b) By adding their wave functions
c) By subtracting their wave functions
d) By creating a new nucleus
Answer: b) By adding their wave functions
12. What is the relationship between the number of bonding and anti-bonding electrons in a molecule and its stability?
a) More anti-bonding electrons lead to higher stability
b) More bonding electrons lead to higher stability
c) More unpaired electrons lead to higher stability
d) The number of electrons does not affect stability
Answer: b) More bonding electrons lead to higher stability
13. In which of the following molecules do the π molecular orbitals result from the side-by-side overlap of p orbitals?
a) H₂
b) HF
c) O₂
d) NaCl
Answer: c) O₂
14. What is the bond order of a molecule with 10 bonding electrons and 4 anti-bonding electrons?
a) 3
b) 2
c) 1
d) 0
Answer: a) 3
15. Which molecular orbitals are formed from the side-by-side overlap of p orbitals?
a) Sigma and pi orbitals
b) Bonding and anti-bonding orbitals
c) Pi and anti-bonding orbitals
d) Sigma and non-bonding orbitals
Answer: c) Pi and anti-bonding orbitals
16. How do molecular orbitals differ from atomic orbitals in terms of energy?
a) Molecular orbitals are always higher in energy
b) Molecular orbitals are always lower in energy
c) Molecular orbitals can be both higher and lower in energy
d) Molecular orbitals have the same energy as atomic orbitals
Answer: c) Molecular orbitals can be both higher and lower in energy
17. What type of bond is present in the molecule N₂ (Nitrogen)?
a) Single sigma bond
b) Single pi bond
c) Double sigma bond
d) Triple bond with one sigma and two pi bonds
Answer: d) Triple bond with one sigma and two pi bonds
18. In a diatomic molecule, what is the shape of the bonding molecular orbitals derived from the p orbitals?
a) Spherical
b) Dumbbell-shaped
c) Two lobes with a nodal plane
d) Four lobes
Answer: c) Two lobes with a nodal plane
19. Which molecule is paramagnetic due to the presence of unpaired electrons?
a) N₂
b) O₂
c) CO
d) F₂
Answer: b) O₂
20. In the molecular orbital theory, what is the bond order of a molecule with 4 bonding electrons and 2 anti-bonding electrons?
a) 1
b) 2
c) 3
d) 4
Answer: b) 1
21. Which of the following pairs of molecules exhibits a bond order of 2?
a) H₂ and He₂
b) O₂ and N₂
c) F₂ and N₂
d) CO and H₂O
Answer: b) O₂ and N₂
22. In which type of molecular orbital does electron density lie between the two nuclei of the bonded atoms?
a) Anti-bonding molecular orbital
b) Non-bonding molecular orbital
c) Bonding molecular orbital
d) Core molecular orbital
Answer: c) Bonding molecular orbital
23. What is the key feature of anti-bonding molecular orbitals?
a) They stabilize the molecule
b) They have a nodal plane between the nuclei
c) They enhance the bond strength
d) They have no nodal planes
Answer: b) They have a nodal plane between the nuclei
24. Which molecular orbital theory principle applies to the distribution of electrons in molecular orbitals?
a) Hund’s Rule
b) Pauli Exclusion Principle
c) Aufbau Principle
d) Heisenberg Uncertainty Principle
Answer: b) Pauli Exclusion Principle
25. What type of bond results from the overlap of orbitals along the axis connecting two nuclei?
a) Pi bond
b) Sigma bond
c) Delta bond
d) Ionic bond
Answer: b) Sigma bond
26. Which molecular orbital is higher in energy compared to the p orbitals of the individual atoms?
a) Bonding sigma orbital
b) Anti-bonding sigma orbital
c) Bonding pi orbital
d) Non-bonding orbital
Answer: b) Anti-bonding sigma orbital
27. What is the bond order of a molecule with equal numbers of bonding and anti-bonding electrons?
a) 1
b) 0
c) 2
d) 3
Answer: b) 0
28. What is the shape of a bonding molecular orbital formed from the overlap of two s orbitals?
a) Spherical
b) Dumbbell-shaped
c) Two lobes oriented along the bond axis
d) Four lobes
Answer: a) Spherical
29. How do the energy levels of bonding and anti-bonding orbitals compare?
a) Bonding orbitals have higher energy than anti-bonding orbitals
b) Bonding orbitals have the same energy as anti-bonding orbitals
c) Bonding orbitals have lower energy than anti-bonding orbitals
d) Energy levels are not applicable in this context
Answer: c) Bonding orbitals have lower energy than anti-bonding orbitals
30. In the molecular orbital theory, how are electrons distributed in a molecule with a bond order of 1?
a) Electrons are equally distributed between bonding and anti-bonding orbitals
b) All electrons are in bonding orbitals
c) There are more electrons in anti-bonding orbitals than in bonding orbitals
d) Electrons are equally distributed among sigma and pi orbitals
Answer: a) Electrons are equally distributed between bonding and anti-bonding orbitals