Question

The cause of periodicity of properties is:
A. Increasing atomic radius.
B. Increasing atomic weight.
C. Number of electrons in the valency orbit.
D. The recurrence of similar outer electronic configuration.

Answer 1

We know that in order to give an appropriate solution to the given question, we are required to understand the basic concept of periodicity which is The periodic repetition of the elements with similar properties after a certain regular interval when atoms are arranged in increasing order of atomic number.

Complete step by step answer:
If explained briefly, the periodic repetition of the elements with similar properties after certain regular interval when atoms are arranged in increasing order of atomic number is called periodicity i.e. when they are arranged in increasing order of their atomic number, elements with similar properties recur at regular intervals in the periodic table and the reason being that after a certain regular interval of time, there is repetition in similar outer electronic configurations which are generally responsible for most of an element's chemical and physical properties, thus resulting I repetition of elements with similar properties.
The elements reoccurring at regular intervals $2,\text{ }8,\text{ }8,\text{ }18,\text{ }18,\text{ }32$ and possess similar properties and thus are grouped in one particular group.

So, the correct answer is Option D.

Note: Note that one is advised to remember and not mistaken between groups and periods of a periodic table as period is basically a horizontal row in a periodic table whereas a group is the vertical column of the periodic table.