The statement that is not correct for periodic classification of elements is

Options

A. The properties of elements are periodic function of their atomic numbers
B. Non-metallic elements are less in number than metallic elements
C. For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals
D. The first ionisation enthalpies of elements generally increase with increase in atomic number as we go along a period

Answer

C

Explanation

In case of transition elements (or any elements), the order of filling of electrons in various orbital is `3p lt 4s lt 3d`. Thus, 3d orbital is filled when 4s orbital gets completely filled.