Question

How many periods are in the periodic table?

Answer 1

Hint: It is a completely factual type question related to the arrangement of periodic table.
- The periods are the horizontally placed sets of elements.

Complete step by step answer:
- In the question it is asked that how many periods are there in the periodic table.This completely a factual type of question about periodic table.From the lower classes we are studying about the periodic table.Periodic table, is the table in which the chemical elements are arranged according to the increasing order of their atomic number.The atomic number represents the number of electrons and number of protons present in the atom of the element,
- We know that there are 118 elements known and these are placed in the periodic table in a specific order.These 118 elements are placed in various groups and periods.A group in a periodic table represents the arrangement of elements in the vertical position ie from top to bottom of the table and in a period, the elements are arranged in a horizontal line fashion from left to right.
- The 118 elements are arranged in 18 groups and 7 periods in the periodic table.
Hence now we know that there are 7 periods in the periodic table.
- The elements in the same period will have the same number of shells and the same valence shells and the number of valence electrons increases by one as we move from left to right of the table,since the atomic number is increasing thereby increasing the number of electrons.
- If we move from left to right across a period the size of the atom is decreasing, since all the elements contains the same number of shells, and the number of electrons and the effective nuclear charge is increasing due to which the valence electrons experiences greater attraction toward the nucleus and thereby the size decreases.
If we move from left to right of the periodic table ,the metallic character decreases and electronegative character is increasing.

Note: The period number is equal to the number of energy levels or the shells available in the atom of an element and the elements placed in the same period does not possess similar chemical properties. If any more elements is to be discovered it will be placed in the eighth period where the concept of g-orbital will be important.