Question

What is a periodic table? How many groups and periods does the modern periodic table have?

Answer 1

Hint: Periodic table is the representation of chemical elements arranged in the trend of some periodic properties. Modern periodic table is the representation of chemical elements in the increasing order of atomic numbers. The chemical elements are arranged in groups and periods.

Complete answer:
Periodic table is the representation of chemical elements arranged according to various trends. Mosley arranged the periodic table in the increasing order of atomic numbers. But, he left some gaps in the periodic table. He named those elements by adding the prefix as eka and the preceding element in that group.
 Mendeleev arranged the periodic table in the increasing order of atomic weights. But, he was not successful in completing the entire periodic table.
Later, a modern periodic table was discovered with the complete elements. The chemical elements are arranged in the increasing order of atomic numbers. These elements are arranged in vertical columns and horizontal rows. The vertical columns are called as groups and horizontal rows are called periods.
There are a total of \[7\] periods and \[18\]groups in the periodic table. Thus, modern periodic tables have \[7\] periods and \[18\]groups.

Note:
The elements are divided into four blocks namely s, p, d and f blocks. The s-block consists of the first two groups. The p-block consists of groups from \[13\] to \[18\]. The d-block consists of groups from \[3\] to \[12\]. But, f-block consists of elements in d-block and known as lanthanides and actinides.