The statement that is not correct for periodic classification of element isA)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 the elements are the periodic function of their atomic numbers
B. Non-metallic elements are lesser in number than the metallic elements
C. the first ionisation energies of elements along a period do not vary in a regular manner with increases in atomic number
D. For transition elements the d-subshells are filled with the electrons monotonically with increases in atomic number.

Answer

D

Explanation

for ionisation elements d-subshell are not filled with electrons monotonically (one at a time) because of extra stability of `d^(5)` and `d^(10)` configurations. Besides these, there are many other exceptions e.g. Nb,Mo,Ru,Rh,Pd,etc.