In the third row of the periodic table,from $Na$ to $Cl$:

The polarity of a covalent bond between two atoms depends upon

Which pair of elements has the maximum electronegativity difference?

Given below are two statements:
Statement $I$: The correct order of electronegativity of fluorine, oxygen and nitrogen is $F > O > N$.
Statement $II$: The oxidation state of oxygen in $OF_2$ is $+2$ and in $Na_2O$ is $-2$.

Which is the correct order of electronegativities?

Among $Me_{3}N$, $C_{5}H_{5}N$ and $MeCN$ $(Me = \text{methyl group})$, the electronegativity of $N$ is in the order: