NEET 2025 MCQ with Answer Explanation : “Molecular Orbital Theory”.

Here below some MCQ’s about “Molecular orbital theory” with answer which is well explained. Let’s check one by one.

1. What does MO stand for in molecular orbital theory?

A) Magnetic Orbital
B) Molecular Orbital
C) Molecule Orbital
D) None of the above

Answer: B

Explanation: MO refers to the molecular orbital, which describes the behavior of electrons in a molecule.

2. Which principle states that electrons occupy the lowest energy orbitals first?

A) Hund’s Rule
B) Pauli Exclusion Principle
C) Aufbau Principle
D) Octet Rule

Answer: C

Explanation: The Aufbau Principle states that electrons fill the lowest available energy levels before occupying higher levels.

3. In which type of molecular orbitals are the electron densities concentrated between the nuclei?

A) Sigma (σ) orbitals
B) Pi (π) orbitals
C) Non-bonding orbitals
D) Antibonding orbitals

Answer: A

Explanation: Sigma orbitals have electron density concentrated along the internuclear axis, promoting bonding.

4. Which molecular orbital is formed by the head-on overlap of atomic orbitals?

A) Pi (π) orbital
B) Sigma (σ) orbital
C) Delta (δ) orbital
D) Sigma star (σ*) orbital

Answer: B

Explanation: Sigma orbitals result from the direct overlap of orbitals, allowing for strong bonding.

5. The bond order of a molecule is defined as:

A) (Number of bonding electrons – Number of antibonding electrons) / 2
B) Number of bonding electrons / Number of antibonding electrons
C) Total number of electrons / 2
D) Number of atoms in the molecule

Answer: A

Explanation: Bond order is a measure of the strength of a bond, calculated using the difference between bonding and antibonding electrons.

6. Which of the following molecules has a bond order of 1?

A) O2
B) N2
C) H2
D) He2

Answer: C

Explanation: H2 has one bond formed by a single pair of electrons, giving it a bond order of 1.

7. What type of molecular orbital results from the side-to-side overlap of p orbitals?

A) Sigma (σ) orbital
B) Pi (π) orbital
C) Delta (δ) orbital
D) Non-bonding orbital

Answer: B

Explanation: Pi orbitals are formed by the lateral overlap of p orbitals, contributing to double bonds.

8. Which of the following statements is true about antibonding molecular orbitals?

A) They stabilize the molecule.
B) They have higher energy than the corresponding bonding orbitals.
C) They contain electron density between the nuclei.
D) They can be occupied by a maximum of two electrons.

Answer: B

Explanation: Antibonding orbitals have higher energy and destabilize the molecule.

9. In which of the following molecules does the bond order equal 0?

A) O2
B) N2
C) He2
D) F2

Answer: C

Explanation: In He2, the bonding and antibonding electrons cancel out, resulting in a bond order of 0.

10. For which of the following species is the bond order 1?

A) B2
B) C2
C) N2
D) O2

Answer: A

Explanation: B2 has a bond order of 1 due to the presence of one bonding pair and no antibonding electrons.