On the basis of quantum numbers, justify that the fourth period of the Modern periodic table should have `18` elements.

Explanation

The basic theme of organisation of elements in the periodic table is to simplify and systematize the study of the numerous properties of all the elements and their compounds. This has been done by arranging the elements in such a way that si nilar elements are placed together while dissimilar elements are separated from one another. This has made the study simple to remember because the properties of the elements are now studied in the form of groups or families having similar properties rather than studying the elements individually,