Chapter 12, Problem 12.93QP

Interpretation Introduction

Interpretation:

The elemental Boron has to be classified in the types of crystalline solids.

Concept Introduction:

• On the basis of the arrangement of the components in a solid, there are two distinct types of solids - crystalline solids and amorphous solids. These two types differ in the arrangement of their respective components and so in their properties.
• Crystalline solids have their own sub-classification. The types of solids can be summarized as follows –

• Crystalline solids have well-defined regular, compact, orderly arrangement of their components of very long range order. They are termed as true solids.
• Amorphous solids lack such well defined arrangement of its components instead disordered or random arrangement does exist in them. They are termed as pseudo solids or super cooled liquids. Example: Glass, Wood etc.
•  Ionic solids, molecular solids, covalent solids, atomic solids and metallic solids are the types of crystalline solids
• In ionic solids, ions of opposite charges are bind together by electrostatic force and are neatly stacked to form a regular and well-defined structure. Example:$\text{KCl}$, Rutile.  They have high melting points and exhibit conductivity only in solvated state. 
• In molecular solid, molecules are arranged in such a fashion and in metallic solid metal atoms are arranged in such a manner. Example: Ice for molecular solid and almost all metals and alloys for metallic solids.  Molecular solids are low melting solids and poor conductors of heat and electricity whereas metallic solids are good conductors of heat and electricity.
• In Covalent solids the components are atoms bonded by covalent bond repetitively and thus forms huge network form of solid. Network solids are widely formed by group 14 elements and its compounds. Example: Diamond, graphite.  They are high melting solids and poor conductors but exceptions prevail.