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

Fill in the blanks:
$(i)$ Atoms and ions having the same number of electrons are known as ........... .
$(ii)$ The quantitative measure of the tendency of an element to lose an electron is called ........... .
$(iii)$ The screening effect is also known by the name ........... .
$(iv)$ The enthalpy change when a gaseous neutral atom forms a negative ion is called ........... .

Given below are two statements:
Statement $I$: The second ionisation enthalpy of $Na$ is larger than the corresponding ionisation enthalpy of $Mg$.
Statement $II$: The ionic radius of $O^{2-}$ is larger than that of $F^{-}$.
In the light of the above statements, choose the correct answer from the options given below.

Maximum number of electrons in the outermost shell of $s, p, d$,and $f$ block elements are respectively:

The statement that is not correct for the periodic classification of elements is

Which element from the following exhibits a diagonal relationship with $Mg$?