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 4 s orbitals
D. The first ionization enthalpies of elements generally increase with increase in atomic number as we go along a period.

Answer

C

Explanation

According to aufbau principle,"in the ground state of the atoms,the orbitals are filled in order of their increasing energies".The increasing order of energy acccording to (n+1) rule is:1s,2s2p,3s,3p,4s,3d,4p,5s….etc.
Therefore,the 3d orbitals are filled with electrons after 4s orbitals and before 4p orbitals.