Use the molecular orbital energy level diagram to show that N2 would be expected to have a triple bond, F2 a single bond and Ne2 no bond.

To understand the bonding behavior of N2, F2, and Ne2 using molecular orbital theory, let's consider their molecular orbital energy level diagrams.

Molecular Orbital Energy Level Diagrams:

1. N2: In the molecular orbital diagram for N2, we have:

    

    

    

   Explanation:

   • The molecular orbital diagram for N2 shows that there are a total of 10 valence electrons (5 from each nitrogen atom).
   • The sigma (σ) bonding orbital formed from the overlap of the 2s orbitals and three sets of 2p orbitals (σ2s, σ2pz, and two σ2px/y) is lower in energy.
   • The pi (π) bonding orbitals formed from the side-to-side overlap of the remaining 2p orbitals (π2px/y) are higher in energy.
   • The highest energy molecular orbital, the π* antibonding orbital, has no electrons.

   Conclusion:

   • Since there are eight electrons occupying the bonding orbitals (σ and π), N2 forms a triple bond.

2. F2: In the molecular orbital diagram for F2, we have:

    

    

    

   Explanation:

   • The molecular orbital diagram for F2 shows that there are a total of 14 valence electrons (7 from each fluorine atom).
   • Similar to N2, F2 has sigma (σ) and pi (π) bonding orbitals.
   • However, due to the presence of additional electrons, the sigma (σ) antibonding orbital (σ*) is now occupied.

   Conclusion:

   • Since there are still eight electrons occupying the bonding orbitals (σ and π), F2 forms a single bond despite the presence of the σ* antibonding orbital.

3. Ne2: In the molecular orbital diagram for Ne2, we have:

    

    

    

   Explanation:

   • The molecular orbital diagram for Ne2 shows that there are a total of 20 valence electrons (10 from each neon atom).
   • Neon is a noble gas with a completely filled valence shell, so all of its valence orbitals are filled.
   • There are no unoccupied or low-energy molecular orbitals available for bonding.

   Conclusion:

   • Since all valence orbitals of Ne2 are completely filled, there is no possibility of bond formation between neon atoms, resulting in no bond formation.

In summary:

• N2 forms a triple bond due to the occupation of sigma (σ) and pi (π) bonding orbitals.
• F2 forms a single bond despite the presence of antibonding orbitals due to the occupation of sigma (σ) and pi (π) bonding orbitals.
• Ne2 does not form a bond due to the completely filled valence orbitals of neon atoms.