Elements A, B, C, D and E have the electronic configura-tion as shown in the table : (i) Name the element which belongs to the 2^(nd) period. (ii) Name two elements which will exhibit a valency of 1. (iii) Name another element which will have the same valency as the element C.

Elements A, B, C, D and E have the electronic configura-tion as shown

1.	Elements A, B, C, D and E have the electronic configura-tion as shown in the table : (i) Name the element which belongs to the 2^(nd) period. (ii) Name two elements which will exhibit a valency of 1. (iii) Name another element which will have the same valency as the element C.
Answer» Solution :(i) The element A belongs to the `2^(ND)` PERIOD since the electrons are filled K and L shells only. (ii) The elements B and D exhibit valency of 1. Valency of element B = 1, Valency of element D = (8 - 7) = 1. (iii) The element A has the same valency as the element C. Valency of element C = (8 - 5) = 3, Valency of element A = 3. THEREFORE, both of them have the same valency.