What are the valence electrons? For s-block and p-block elements show that number of valence electrons is equal to its group number.

What are the valence electrons? For s-block and p-block elements show

1.	What are the valence electrons? For s-block and p-block elements show that number of valence electrons is equal to its group number.
Answer» Electrons present in the outermost shell of the atom of an element are called valence electrons. 3Li is an s-block element and its electronic configuration is 1s²2s¹. Since it has one valence electron, it is placed in group 1. Therefore, for s-block elements, group number = number of valence electrons. However, for p-block elements, group number = 18 – number of electrons required to attain complete octet. 7N is a p-block element and its electronic configuration is 1s²2s²2p³. Since it has five electrons in its valence shell, it is short of three electrons to complete its octet. Therefore, its group number = 18 – 3 = 15.