question_answer 1)

  Metal hydrides are ionic, covalent or molecular in nature. Among\[LiH,\text{ }NaH,\text{ }KH,\text{ }RbH,\text{ }CsH\], the correct order of increasing ionic character is: (a) \[LiH>NaH>CsH>KH>RbH\]                   (b) \[LiH<NaH<KH<RbH<CsH\] (c) \[RbH>CsH>NaH>KH>LiH\]                   (d) \[NaH>CsH>RbH>LiH>KH\]

Answer:

  (b) The ionic nature increases as the electro negativity difference increases from Li to Cs. \[\underset{1.1}{\mathop{LiH}}\,~~~\underset{1.2}{\mathop{NaH}}\,~~~\underset{~1.3}{\mathop{~KH~}}\,~~\underset{1.3}{\mathop{RbH}}\,~~~~\underset{~~1.4}{\mathop{CsH}}\,\]