11th Class Chemistry The p-Block Elements-I

  • question_answer 87)   Describe the general trends in the following properties of the groups 13 and 14. (i) Atomic size (ii) Ionisation enthalpy (iii) Metallic character (iv) Oxidation states (v) Nature of halides

    Answer:

       

      Property Group 13 Group 14
    1. Atomic size With the exception of gallium, the atomic size in-creases from boron to thallium. \[\underset{85pm}{\mathop{B}}\,\,\,\,\underset{143}{\mathop{Al}}\,\,\,\,\underset{135}{\mathop{Ga}}\,\,\,\,\underset{167}{\mathop{\ln }}\,\,\,\,\underset{170}{\mathop{Tl}}\,\] Atomic size increases gradually from carbon to lead. \[\underset{77}{\mathop{C}}\,\,\,\,\,\underset{118}{\mathop{Si}}\,\,\,\,\underset{122}{\mathop{Ge}}\,\,\,\,\underset{140}{\mathop{Sn}}\,\,\,\,\underset{146pm}{\mathop{Pb}}\,\]
    2. Ionisation enthalpy A regular decreasing trend is not observed in first ionisation enthalpy. \[\begin{array}{*{35}{l}}    In<Al<Ga<Tl<B  \\ \end{array}\] First ionisation enthalpy de- creases from carbon to tin. \[\begin{array}{*{35}{l}}    Sn\text{ }<\text{ }Pb\text{ }<\text{ }Ge\text{ }<\text{ }Si\text{ }<\text{ }C  \\ \end{array}\]
    3. Metallic character Metallic nature increases from boron to aluminium, then decreases from aluminium to thallium. Increases gradually on moving down the group.
    4. Oxidation states +3 and +1 oxidation states the stability of +1 increases while that of +3 decreases on moving down the group. +4 and +2 oxidation states the stability of +2 increases while that of +4 decreases on moving down the group.
    5. Nature of halides All form trihalides of the type \[M{{X}_{3}}\] the stability decreases from boron to thallium. Thallium also forms stable\[TlCl\]. All form tetrahalides of the type\[M{{X}_{4}}\]. Stability decreases. \[Ge,\text{ }Sn\]and \[Pb\]also form dihalides, \[M{{X}_{2}}\]. Stability increases.


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