Question

Why was there no zero four in the original Mendeleefs Periodic Table?

Answer 1

Medeleev presented his periodic table on 6 March 1869.

Pierre Janssen and Joseph Norman discovered Helium on August 18,1968 while looking at chromosphere of the sun.Noble gases Helium and Argon were accepted as elements only by the end of nineteenth century.They were included as zero group elements by Mendeleev in periodic table in 1902.