question_answer 33)

Explain : (a) The basis of similarities and differences between metallic and ionic crystals. (b) Ionic solids are hard and brittle.  

Answer:

(a) The basis of similarities between the metallic and ionic crystals are the electrostatic forces of attraction. These arc present among the ions in the ionic crystals and among the kernels and valence electrons in the metallic crystals. That is why both metals and ionic compounds are good conductors of electricity and have high melting points. The basis of difference is the absence of mobility of ions in the ionic crystals while the same is present in the valence electrons in case of metallic crystals. As a consequence, the ionic compounds conducts electricity only in the molten state while the metals can do so even in the solid state. (b) The ionic solids are hard and brittle because of strong electrostatic forces of attraction which are present in the oppositely charged ions.