Question

how to find group and period of an elements

Answer 1

Answer:

The number of shells in the electronic configuration of the given element determine it's period i.e. if there are 3 shells in an atom then it will belong to period 3.

The number of valence electrons in the atom determines the group number of that atom i.e. if an element has 4 valence electrons then it must belong to group IV A.

Let us take an example:

Element: Sodium

Symbol: Na

Electronic Configuration: 2, 8, 1

Since sodium has 3 shells, it belongs to period 3. Also, we notice that this element has 1 electron in its outermost orbit therefore it belongs to group I A.

Hence, Sodium is present in group IA of period 3 in the modern periodic table.