Question

how to count sigma and pi bond ,please see question no 1​

Answer 1

1.  there two pi bonds and one sigma bond in N2. .

reason (not confirmed) :  N2  is fairly simple; since nitrogen is atomic number  7, it has an electron configuration of  1s22s22p3

, so it favorably shares its three  2

p  electrons with three other  2

p  electr.ons from another nitrogen to form a noble gas configuration ( 1s22s22p6).

Since all three  

2p  orbitals participate,  we form one  2pz−2pz  head-on (σ) interaction, one  2px−2px  sidelong (π) interaction, and one  2py−2py  sidelong (π) interaction.

Thus, we form a triple bond, which consists of the one  (σ

) and two(  π)  bonds we just mentioned. The remaining two lone pairs of electrons are stored in each nitrogen's  2

s  orbital. So, we get the following structure that illustrates this discussion:

3. O2  has 1 sigma bond and 1 pi bond.

reason :   the  O2  molecule's Lewis structure shows a double bond between the two oxygen atoms.  Always remember that a double bond is comprised of 1 sigma bond and 1 pi bond. A triple bond has 1 sigma and 2 pi bonds.