question_answer

Elements with atomic numbers 17 and 20 form compounds with hydrogen. Write the formulae of the two compounds and compare their chemical behaviour in water.

Answer:

                The elements with atomic numbers 17 and 20 are chlorine and calcium. Their corresponding hydrides are \[HCl\] and \[Ca{{H}_{2}}\]. While \[HCl\] dissociates in water to give acidic solution, \[Ca{{H}_{2}}\] reacts with water to evolve hydrogen gas and the resulting solution is basic in nature. \[HCl\xrightarrow{(aq)}\,{{H}^{+}}(aq)+C{{l}^{-}}(aq)\] \[Ca{{H}_{2}}+2{{H}_{2}}O\xrightarrow{\,}\,Ca{{(OH)}_{2}}\,+{{H}_{2}}\].