Question

Why are ionic compounds usually hard?

Answer 1

Hint: Attempt his question by explaining the formation of an ionic bond and how it is made. Also, explain the property of its constituent elements and the kind of attractive force acting between them.

Complete step by step answer:
Ionic compounds are defined as,” The crystalline solids formed by neatly packed ions of opposite charge. Ionic compounds are usually formed when metals react with non-metals”.
In ionic compounds, a metal loses electrons and nonmetal gains electrons to complete its valence shell, to achieve stability (i.e. has the configuration of the nearest noble gas). The respective metal and non-metal ions are bound by ionic bonds, which is an electrostatic force of attraction between a positive and a negative charge (i.e. cation and anion). This electrostatic force is the main reason for hardness of ionic compounds.
The oppositely charged ions in an ionic compound are packed tightly with each other and form a crystalline structure which is very hard and rigid.
For example – In the formation of NaCl, Sodium (Na) loses an electron and Chlorine (Cl) gains an electron to form an ionic bond.
\[\begin{align}
  & Na\to N{{a}^{+}}+{{e}^{-}} \\
 & Cl+{{e}^{-}}\to C{{l}^{-}} \\
 & N{{a}^{+}}+C{{l}^{-}}\to NaCl \\
\end{align}\]

Additional Information: There are three types of bonds formed between elements – Ionic, Covalent and Coordinate.

Note: Some of the other properties shown by ionic compounds includes –
Ionic compounds are brittle in nature, they are hard to break.
Ionic compounds have high melting and boiling points (a large amount of energy is required to break the ionic bonds between the atoms).
Ionic compounds are soluble in polar solvents (such as water whereas), whereas solubility tends to decrease in non-polar solvents.
Ionic compounds do not conduct electricity in the solid-state but are good conductors in an aqueous state.