(a) List two advantages of adopting the atomic number of an element as the basis of classification of elements in the Modern Periodic Table. (b)…

Atomic number is more fundamental property and it decides the properties of an element.

Atomic number increases by one in going from one element to the next, so arrangement of elements becomes more systematic.

Prediction of properties of elements could be made with more precision when the elements are arranged in increasing order of their atomic numbers.

(b) Electronic configuration of X - $\displaystyle 2$, $\displaystyle 8$, $\displaystyle 3$ Electronic configuration of Y - $\displaystyle 2$, $\displaystyle 8$, $\displaystyle 8$, $\displaystyle 2$