Which one of the following species does not exist?

1. ${\mathrm{Be}}_2^{+}$

2. Be₂

3. B₂

4. N₂

Which one of the following is not paramagnetic ?

1. NO

2. ${\mathrm{N}}_2^{+}$

3. CO

4. ${\mathrm{O}}_2^{-}$

According to molecular orbital theory, arrange the nitrogen species in each list in ascending order of bond order:

1. ${\mathrm{N}}_2^{-}<mspace\; width="1em"></mspace><<mspace\; width="1em"></mspace>{\mathrm{N}}_2<mspace\; width="1em"></mspace><<mspace\; width="1em"></mspace>{\mathrm{N}}_2^{2-}$

2. ${\mathrm{N}}_2^{2-}<mspace\; width="1em"></mspace><<mspace\; width="1em"></mspace>{\mathrm{N}}_2^{-}<mspace\; width="1em"></mspace><<mspace\; width="1em"></mspace>{\mathrm{N}}_2$

3. ${\mathrm{N}}_2<mspace\; width="1em"></mspace><<mspace\; width="1em"></mspace>{\mathrm{N}}_2^{2-}<mspace\; width="1em"></mspace><\hspace{0.17em}{\mathrm{N}}_2^{-}$

4. ${\mathrm{N}}_2^{-}<mspace\; width="1em"></mspace><<mspace\; width="1em"></mspace>{\mathrm{N}}_2^{2-}<mspace\; width="1em"></mspace><<mspace\; width="1em"></mspace>{\mathrm{N}}_2$

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

1. Be₂ is not a stable molecule

2. He₂ is not a stable but He_2⁺ is expected to exist.

3. Bond strength of N₂ is maximum amongst the homonuclear diatomic molecules belonging to the second period.

4. The order of energies of molecular orbitals in N₂ molecule is

 s2s < s*2s < s2p_z < (p2p_x=p2p_y) < (p*2p_x=p*2p_y) < s*2p_z  

In the molecular orbital diagram for ${\mathrm{O}}_2^{+}$ ion. the HOMO is :-

(1) $\sigma$ MO orbital

(2) π MO orbital

(3)  π^* MO orbital

(4) $\stackrel{*}{\sigma }$ MO orbital