Yes it is true.The dz2 orbital has a lob along z axis and a electron ring in the xy plane. This particular shape arises due to constraints of angular momentum placed on the wave function. A proper answer could be given depending upon your level of study.For a basic level of study just draw the shape of dz2 orbital and just say that this is how the electron cloud was found from experiments. An exact answer would require you to work out the shape from the wave function subjecting it to proper constraints.
Question : What is $\frac{\left (x^{2}-y^{2} \right)^{3}+\left (y^{2}-z^{2} \right )^{3}+\left (z^{2}-x^{2} \right )^{3}}{\left (x-y \right)^{3}+\left (y-z \right )^{3}+\left (z-x \right)^{3}}?$
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