Question

The term periodicity is the properties of elements, which are arranged in the increasing order of their atomic numbers. Then the elements with similar properties:
A. Reoccur after a fixed interval
B. Reoccur after certain regular interval
C. Form vertical groups
D. Form horizontal rows

Answer 1

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.
Elements reoccurring at regular intervals of $2,8,8,18,18,32$ possess similar properties and thus are grouped in one particular group.
For instance, Elements with atomic numbers $1,3,11,19,37,55,87$ are having similar properties as explained.

Therefore, the correct option would be (B) Reoccur after a certain regular interval.

Note: 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.