Question

Which of the following statements is not correct from the view point of molecular orbital theory?

• A. $B{e}_2$ is not a stable molecule.
• B. $H{e}_2$ is not stable but $H{e}_2^{+}$ is expected to exist.
• C. Bond strength of $N_2$ is maximum amongst the homonuclear diatomic molecules belonging to the second period.
• D. The order of energies of molecular orbitals in $N_2$ molecule is $\sigma 2s<\sigma \ast 2s<\sigma 2p_z<(\pi 2p_x=\pi 2p_y)<(\pi \ast 2p_x=\pi 2p_y)<\sigma \ast 2p_z$

Answer 1

The correct option is D The order of energies of molecular orbitals in $N_2$ molecule is $\sigma 2s<\sigma \ast 2s<\sigma 2p_z<(\pi 2p_x=\pi 2p_y)<(\pi \ast 2p_x=\pi 2p_y)<\sigma \ast 2p_z$

1. $B{e}_2$ has bond order zero , so it is not stable molecule,

2. $H{e}_2$ has bond order zero and $H{e}_2^{+}$ has bond order 1

3.Bond strength of $N_2$ is maximum as the bond order is $3$ that is maximum amongest the homonuclear diatomic molecules belonging to the the second period.

4.The correct order of the energy of molecular orbital for$N_2$ is $\sigma 2s<\sigma \ast 2s<(\pi 2p_x=\pi 2p_y)<\sigma 2p_z<(\pi \ast 2p_x=\pi \ast 2p_y)<\sigma \ast 2p_z$

So the correct option is $D$.