Diagonal relationship is shown by

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 $[Kr] 4d^8 5s^2$.

Which of the following orders is correct according to the given property?

Fluorine,chlorine,bromine and iodine are placed in the same group $(17)$ of the periodic table,because

How many of the following statements are correct?
$(a)$ 'He' is the second most abundant element in the universe.
$(b)$ The symbol for the element with atomic number $110$ is Ds.
$(c)$ Osmium has the highest density among all elements.
$(d)$ Francium is the most electropositive element in the periodic table.

Which property decreases from left to right across the periodic table and increases from top to bottom?
$(i)$ Atomic radius
$(ii)$ Electronegativity
$(iii)$ Ionisation energy
$(iv)$ Metallic character