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

(i) Be2 is not a stable molecule.

(ii) He2 is not stable but He2 + is expected to exist.

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

(iv) The order of energies of molecular orbitals in N2 molecule is

σ2s < σ* 2s < σ2p_z < (π2p_x = π2p_y ) < (π*2p_x = π* 2p_y) < σ* 2p_z

<p>This is a Multiple Choice Questions as classified in NCERT Exemplar</p><p><strong>Ans:</strong> Option (iv)</p><p><strong> (a)</strong> A molecule which has a zero bond order never exists and a molecule having a non-zero bond order either exists or is expected to exist.</p><p><strong> (b)</strong> If the value of bond order is high then the bond strength will also be higher. Electrons present in the bonding molecular orbital are known as the bonding molecular orbital ( N_b ) and the electrons present in the anti-bonding molecular orbital are known as anti-bonding electrons ( N_a ). The half of the difference of bonding and anti-bonding electrons is known as the bond order.</p><p>The bond order of Be₂ : Be₂=s 1s2, s *1s², s 2s², s*2s²</p><p>The bonding and anti-bonding electrons are both 4 . Then the bond order (BO) will be:</p><p>BO= (4-4)</p><p>BO= 0</p><p>Bond order of Be₂ is zero. So, it does not exist.</p>

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