The first element of a group differs in many ways from the other heavier members of the group due to:

Which of the following statements are correct for the classification of elements?
$I$. The properties of elements are periodic functions of their atomic numbers.
$II$. Non-metallic elements are less in number than the metallic elements.
$III$. The first ionisation energies of elements along a period do not vary in a regular manner.
$IV$. The ground state electronic configuration of $Pd (Z=46)$ is $[Kr] 4d^8 5s^2$.

In which of the following sets,elements are not correctly arranged with the property shown in brackets?

Represent different types of periodic properties in the periodic table.

Which elements in groups $1$ to $17$ differ in many respects from the other elements of their respective groups?

Which of the following properties does not depend on periodicity?