Periodicity | Periodic classification#

Periodic Classification#

There are about 118 elements discovered by the scientists so far.
Due to such a large number of elements, it is very difficult to study the properties of each element separately.
Periodic classification is a method of grouping similar elements together and separating them from dissimilar elements.
In this lesson, we will mainly focus on the modern periodic table.

Modern periodic law, given by Henry Moseley, states that "The physical and chemical properties of the elements are periodic functions of their atomic numbers."
Atomic number is defined as the nuclear charge or the number of protons or the number of electrons in neutral atoms.
The horizontal rows in periodic table are called periods and the vertical columns are called groups.
There are altogether seven periods. The period number corresponds to the highest principal quantum number (n) of the elements in the period. The first period contains 2 elements. The subsequent periods consists of 8, 8, 18, 18 and 32 elements, respectively.
The seventh period is incomplete and theoretically, it will have a maximum of 32 elements.
Elements having similar outer electronic configurations in their atoms are arranged in vertical columns, referred to as groups or families. There are 18 groups in total.