Comprehension given below is followed by some multiple choice question, Each question has one correct options. Choose the correct option.
Molecular orbitals are formed by the overlap of atomic orbitals. Two atomic orbitals combine to form two molecular orbitals called bonding molecular orbital (BMO) and anti-bonding molecular orbital (ABMO). Energy of anti-bonding orbital is raised above the parent atomic orbitals that have combined and hte energy of the bonding orbital is lowered than the parent atomic orbitals.
energies of various molecular orbitals for elements hydrogen to nitrogen increase in the order
`sigma1s lt sigma^(star)1s lt sigma^(star)2s lt ((pi2p_(x))=(pi2p_(y))) lt sigma2p_(z) lt (pi^(star)2p_(x) = pi^(star)2p_(y)) lt sigma^(star)2p_(z)` and For oxygen and fluorine order of enregy of molecules orbitals is given below.
`sigma1s lt sigma^(star)1s lt sigma2s lt sigma^(star)2s lt sigmap_(z) lt (pi2p_(x) ~~ pi2p_(y)) lt (pi^(star)2p_(x)~~ pi^(star)2py) lt sigma^(star)2p_(z)`
Different atomic orbitalsof one atom combine with those atoms orbitals of the second atom which have comparable energies and proper orientation.
Further, if the overlapping is head on, the molecular orbital is called sigma, `sigma` andif the overlap is lateral, the molecular orbital is called pi, `pi`. The molecular orbitals are filled with electrons according to the same rules as followed for filling of atomic orbitals.
However, the order for filling is not the same for all molecules or their ions. Bond order is one of the most important parameters to compare the strength of bonds.
67) Which of the following pair is expected to have the same bonod order?

Options

A. `C_(2)`
B. `B_(2)`
C. `O_(2)`
D. `Be_(2)`

Answer

C

Explanation

For all elements which have atomic number more than 7 (beyond nitrogen ) the energy of `sigma2p_(z)` is lower than `pi 2p_(x) and pi 2p_(y)`- orbitals.