Question

shape of a complex will be square planar if its coordination number is ?

Answer 1

Square planar if the co ordination number is 4.... And usually the hybridization will be $dsp^{2}$

Answer 2

Square of a (chemical compound) complex can be square planar when the coordination number of the central atom is 4.  The central atom is bonded to 4 ligands (atoms or molecules or ions) at symmetrical positions around it, in a plus like geometry.  The centers of the central atom and the ligands are in one single plane.

In some special cases compounds with central atom has coordination number 4, but it is in tetrahedral shape.  It depends on the actual electronic configuration and sizes and dipole moments of the ligands present.