question_answer 56)

    Three elements A, B and C have 3, 4 and 2electrons respectively in their outermost shell. Give the group number to which they belong in the modern periodic table. Also, give their valencies.

Answer:

                  (i) Element A has 3 valence electrons, therefore, its valency is 3 and thus belongs to group13 (3 + 10). As such it could be any one of the following elements: B, Al, Ga, In or Tl. (ii) Element B has 4 valence electrons, therefore, its valency is 4 and it belongs to group 14(4 + 10). The element B could be any one of the following: C, Si, Ge, Sn or Pb. (iii) Element C has two valence electrons, therefore, its valency is 2 and it belongs togroup2. The element C could be any one of the following: Be, Mg, Ca, Sr, Ba or Ra.