Explain why both square planar and tetrahedral complexes have coordination number=4, and yet square planar complexes can never be chiral while tetrahedral complexes can.

The coordination number is 4.  

Explanation:

Square planar clusters can be either cis or trans, as they form 180 and 90-degree bond angles. Therefore, a pair of ions may be adjacent (cis) to one another and immediately across (trans) from one another. A square planar molecule could never be simultaneously cis and trans, so because several coordinators are 4. Since linear complexes have only an angle of a bond of 180 degrees, they can not have cis or trans-isomers. In the coordination complex, there is only yet another way possible of bonding the two binding sites to the steel.