question_answer

                  (a) Complete and balance the following equation (i)         (ii) (iii)           (iv) (v)     (vi) (b) Arrange the following in increasing order of basicity.

Answer:

  (i) Oxygen and sulphur are non - metals Se and Te are metalloids whereas Po is a metal. Po is radioactive elements and its half life is 13.8 days. The metallic character increases from oxygen to polonium. (ii) Among O, S, Se, Te. Sulphur has strong tendency to show catenation property it decreases down the group. All the elements form hydrides of the type  [E - O, S, Se, Te, Po]. Since down the group bond dissociation enthalpy decreases therefore the thermal stability of hydride also decreases from  to . (iv) Oxygen shows negative oxidation state - 2 except in  its oxidation state is +2. Polonium hardly shows negative oxidation state. Its stability decreases down the group. Other elements of the group exhibit + 2, + 4 and + 6 oxidation states Se, Te show + 4 0. S in their compounds with oxygen and + 6 with fluorine. The stability of + 6 O.S decreases down the group and stability of + 4 O.S increases due to inert pair effect. Bonding in + 4 and + 6 oxidation state is primarily covalent. (v) All the elements show allotropy.