Question

How does the electronic configuration of an atom relate to its position in the modern periodic table?

Answer 1

The total number of electron shells in an atom determines the period to which the element belongs, and the valence electrons determine the group to which it will belong. So with the help of electronic configuration we can figure out the period and group number of an element

Elements with one and two valence electrons belong to group 1 and 2 respectively, while to determine the group number of elements with 3 to 8 valence electrons, we add 10 to their valence electrons

For example an element X has atomic number 15
Its configuration will be:
K shell has 2 electrons, L will have 8, and the remaining 5 will be placed in M shell
Since it has three shells it belongs to period 3 and with 5 valence electrons the element will be placed in five plus ten that is the 15th group
So with the help of electronic configuration we can figure out the period and group number of an element.