Sorry i have written my question wrong , here is the corrected version

Let us consider a scenario , Two imaginary same atoms (A^{1} and A^{2} )with different hybridization (both are isolated and far apart from each other ) say one has sp another has sp^{2} .

Sp2 atom will be stable when it's bond angle between all 3 atoms is 120° and sp will be stable when it has 180° . (Here we were considering whole system , in case of calculating potential energy we have to sum the potential energy due to all possible repulsion

)

What if one of the bond angle between SP2 hybridized atom has 180° (Just reshape it and forget about other 2 bonds ) , It will make the whole system unstable but i am not worried about it .

What if we only consider the potential energy due to repulsion between angle b_{1}A^{2}b_{2} and a_{1}A^{1}a_{2} . Which one will have higher potential energy ??

I got my answer from my primary knowledge of bonds (which i have done in my high school ) , we used to take help of a term known as ANGLE STRAIN .

So I thought to apply , and I applied. It's quite simple there is a angle strain in Sp2 hybridized atom so it should have higher potential energy.

But I felt into more deeper and basic questions , They challenged my previous understandings . SO here we go ,

This term known as Angle strain , where did it come from ?? i reached on conclusion that it arouse from the summation of the potential energy of all possible interaction . Am i right ??

do we really consider angle Strain due to Increase in repulsion ??

or Bonds really act as a hard sticks , on bending them there is a increase in potential energy.

what's the matter ??

Simply answer me Why we consider angle strain ??