In the formation of a chlorine molecule, $3{\mathrm{p}}_{\mathrm{z}}$ orbital of one chlorine molecule overlaps with the $3{\mathrm{p}}_{\mathrm{z}}$ orbital of another chlorine atom.

What is the total number of sigma and pi bonds in the following molecule?

 ${\mathrm{C}}_2{\mathrm{H}}_2$ 

What is the total number of sigma and pi bonds in the following molecule?

${\mathrm{C}}_2{\mathrm{H}}_4$

How many bonds are there in:

Considering $\mathrm{x}$-axis as the internuclear axis, which out of the following will not form a sigma bond and why?

(a) $1\mathrm{s}$ and $1\mathrm{s}$ (b) $1\mathrm{s} \mathrm{and} 2{\mathrm{p}}_{\mathrm{x}}$ (c) $2{\mathrm{p}}_{\mathrm{y}} \mathrm{and} 2{\mathrm{p}}_{\mathrm{y}}$ (d) $1\mathrm{s} \mathrm{and} 2\mathrm{s}$.