Question

In how many groups and periods the elements in modern periodic tables are classified?

Answer 1

Hint:
Period of the periodic table means the rows which are horizontal of the plane of your page or board. The group of the periodic table means the columns which are vertical to the rows. The elements of a definite row contain the same number of orbits. The elements of the same column have the same chemical behaviors.

Complete step by step answer:
In the periodic table all the elements are arranged by the atomic numbers. Generally, at the left side of the periodic table, elements are metallic in nature. Moving from left to right the metallic character decreases and non-metallic character increases. At the extreme left elements are non-metallic in nature. There are a total 118 numbers of the elements in the modern periodic table.
This modern periodic table is divided into seven rows and eighteen columns( groups).

Additional information:
In the periodic table the number of the elements in each row are,

row	Number of the elements
1	2
2	8
3	8
4	18
5	18
6	32
7	32

Note:
There are some limitations of modern periodic table, which are,
-The position of the hydrogen is still in confusion as it has similarities with group 1 and group 17 elements.
-Lanthanides and actinides can not be placed in the periodic table due to their similar chemical properties.
-There is no such position for the isotopes in the periodic table.