The statement that is not correct for the periodic classification of element, is a. The properties of elements are the periodic functions of their atomic numbers. b. Non-metallic elements are lesser in number than metallic elements. c. The first ionization energies of elements along a period do not vary in a regular manner with increase in atomic number. d. For transition elements the d-subshells are filled with electrons monotonically with increase in atomic number.

Sol. (a) Correct statement : According to Moseley’s law, the properties of elements are the periodic function of their atomic numbers. (b) Correct statement : The whole s-block, d-block, f-block and heavier p-block elements are metal. (c) Correct statement : Trent is not regular, Be has higher first ionization energy than B, nitrogen has higher first ionization energy than oxygen. (d) Wrong statement : d-subshells are not filled monotonically, regularity break at chromium and copper.