Periodic Elements related doubt

Question

why are the 4 elements in the periodic table have not been found?

Answer 1

I'm sorry, but, as stated, this question does not seem to make sense.  Is something missing, Prashant?

Answer 2

The nuclei of some elements are so unstable that they decay very rapidly and therefore exist for extremely short periods of time before radioactive disintegration.  Hence, they are not observed occurring naturally, although they may be observed very briefly as transient products in nuclear physics experiments.