Question

Give the number of periods and groups in the Modern Periodic Table.

Answer 1

Periodic table can be defined as the collective arrangement of all the elements present. The arrangement is based on the increasing or decreasing order of different properties of these elements. By referring to the periodic table, one can get much information about the properties of elements.

Complete step by step answer:
In Mendeleev’s periodic table, he arranged elements in the order of atomic mass. He believed that all the properties of the element including physical and chemical depend on the mass number. The mass number, as we know, is the sum of neutrons and protons present in the nucleus of an atom.
There were many limitations to Mendeleev’s Periodic Table and from this, the Modern Periodic Table was made.
We can see that elements in the Modern Periodic Table are arranged in the order of their increasing atomic number. Atomic number as we know is the number of protons present in the nucleus of an atom.
There is the vertical arrangement of the elements in the periodic table and it is known as a Group whereas the horizontal arrangement is called the Period.
For all the elements in a period, the valence shell electrons are present in the same orbital whereas on going down the group, a new shell is added to every atom.
There are a total of 7 periods and 18 groups in the Modern Periodic Table.

Note: The position of an element in a modern periodic table can be found out using the electronic configuration or by knowing the atomic number. The number of shells of an atom is linked to the period. For example, Sodium with electronic configuration 2,8,1 has 3 shells. So we can say that it belongs to the 3rd period.
Similarly, the number of valence electrons present in an atom says about the group in which that particular element is placed. The valence electrons in Sodium is 1. So we can say it is present in the 1st group.
Thus, the position of Na in the periodic table is Group 1 and Period 3.