What is the average bond order of the hypothetical molecule Ar₂?

• A. 0.5
• B. 1
• C. 0
• D. 2

Answer: (C)

Verified step by step guidance

1. Recall that bond order is defined as half the difference between the number of bonding electrons and antibonding electrons: \[ \text{Bond order} = \frac{(N_b - N_a)}{2} \] where \(N_b\) is the number of electrons in bonding molecular orbitals and \(N_a\) is the number of electrons in antibonding molecular orbitals.
2. Consider the electronic configuration of the argon atom (Ar), which has 18 electrons. For the diatomic molecule Ar₂, the total number of electrons is 36.
3. Construct the molecular orbital (MO) diagram for Ar₂ by filling the molecular orbitals with 36 electrons, starting from the lowest energy bonding orbitals to the higher energy antibonding orbitals, following the Pauli principle and Hund's rule.
4. Count the total number of electrons in bonding orbitals (\(N_b\)) and antibonding orbitals (\(N_a\)) after filling all 36 electrons in the MO diagram.
5. Calculate the bond order using the formula from step 1. Since Ar₂ is a noble gas dimer with filled bonding and antibonding orbitals, the bond order will be zero, indicating no net bond formation.