Question

$\textbf{Define the following terms }$:

1. Period

2. Periodicity

3. Identity element

4. Inverse element.

Answer 1

Period :- the seven rows drawn downwards in the modern periodic table are known as periods.

Answer 2

1.$\textbf{Period}$:

The recurring part of a non-terminatting recurring decimal is called period.

2. $\textbf{Periodicity}$:

The number of digit in the recurring part of the decimal is called its periodicity.

3 and 4th are in attachment