Question

In KO2 and Na2O2, to find bond order, why we need to break the molecules first. And after breaking, why we only consider electrons of Oxygen to find bond order? Pls show me how to find their bond order. Thanks

Answer 1

According to the molecular orbital theory, the alpha and gamma orbit can have only 2 electrons. So this theory does not accommodate with 20 electrons. 

As number of sodium atoms are 11 so number of electrons will be 22
So for finding the bond order O2 will be considered

As the number of potassium are 19, the nmber of electrons will be 38. In this case we will consider O2 also. As the atomic number of O2 is 18

Bond order: 1/2 (Nb - Na)

Nb= number of electron in bonding molecular orbital 
Na= number of electrons in anti bonding molecular orbital
 
or O2
б1s²б'1s²б2s²б'2s²б2pz² (λ2pz² = λ2py²) (λ2py¹ = λ'2py¹)
Nb= 10
Na = 6
BO = 1/2(10-6)
= 4/2 
=2

Answer 2

Answer: as na is a metal and o is non metal thus na2o2 will make ionic bond

when we dissociate na2o2 then product will be na2^2+ and o2^2-

as molecular confriguration of o2 contain 8 bonding electrons and 6 anti bonding electron

thus using formula=  

bonding e-anti B.E /2

we can find bond order and bond order of oxygen is 1.

Explanation: