Option (b)
Zirconium belongs to group IV and 5th period of the periodic table. The electronic configuration is [tex][Kr]4d^{2}5s^{2}[/tex] here, Kr belongs to 18th group (noble gas) with atomic number 36 and electrons per shell is 2, 8, 18, 8.
Since, atomic number is equal to number of protons and number of electrons, atomic number of zirconium will be 36+2+2=40.
Thus, atomic number of zirconium is 40.
