The statement that is not correct for periodic classification of element is
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 electron 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

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 orbitals is 3p lt 4s lt 3d. Thus, 3d orbital is filled when 4s orbital gets completely filled.