What is the significance of atomic number in the modern classification of elements? Explain with the help of an example.
The significance of atomic numbers in the modern periodic table is that it helps in arranging the elements according to their electronic configuration. Since, the number of valence electrons is the same, elements placed in the same group show similar chemical properties.
For example, if we take the element lithium (Li), its atomic number is 3. Its electronic configuration is (2,1). As it has one valence electron, it is placed in the first group of the periodic table. Similarly, all the elements having one valence electron will be placed in group 1, and they show similar chemical properties. In this manner, classification of elements is made according to the electronic configuration of the elements.