Question

(a) What do you mean by valence electrons? 

(b) Write the electronic configurations of element K(19) ad N(7). 

(c) Write the number of valence electrons in each of these elements. 

Answer 1

(a) The number of electrons present in the outermost shell of an atom is known as valence electrons. For e.g., 

the electronic configuration of Na (11) is              K  L  M

                                                                             2  8  1

Thus, the number of valence electrons present in Na is 1.

                                                                     . K L M N 

(b) Electronic configuration of K (19) =          2 8 8 1 

Electronic configuration of N (7) =                 2 5 

(c) No. of valence electrons in K (19) = 1 (as 1 electron is present in last shell) 

No. of valence electrons in N (7) = 5 (as 5 electrons is present in last shell)