Question

What is the cause of periodicity in the properties of the elements? Explain with two examples.

Answer 1

Hint: Elements in the periodic table are arranged in the increasing number of electrons and there is an electronic configuration of elements that can help to find the group and many properties of the elements.

Complete answer:
There are many elements that are difficult to study, so there is a periodic table that helps us to learn these elements in an easier way. Elements in the periodic table are arranged in the increasing number of electrons and there is an electronic configuration of elements that can help to find the group and many properties of the elements.
When atoms are grouped in order of increasing atomic numbers, the properties of the elements are replicated after such frequent intervals, according to the Modern Periodic Law. Furthermore, a close inspection of the electronic configurations of different elements reveals that with an increase in atomic number, a similar outer electronic configuration is repeated at frequent intervals. By combining these two results, we can deduce that the repetition of a related exterior structure at regular intervals is the source of the periodicity of properties.
For example, all alkali metals in group IA have an outer electronic configuration identical to $n{{s}^{1}}$, where n is the number of outermost principal shells.
Similarly, all halogens, i.e., group VIIA elements, have similar other electronic configurations which are identical to $n{{s}^{2}}n{{p}^{5}}$ and thus have similar properties.

Note:
Only after a certain daily interval does the electronic arrangement of alkali metals repeat. 2, 8, 8, 18, 18, and 32 are the regular cycles. The term "magic number" refers to these figures.