CBSE · Class 10 · Science · Metals and Non-metalsExplain the formation of Magnesium Chloride ($\text{MgCl}2$) by the transfer of electrons. State two general physical properties of ionic compounds.

Formation of Magnesium Chloride ($\text{MgCl}_2$):

1. Magnesium atom:

   • Atomic number = 12
   • Electronic configuration = 2, 8, 2
   • To achieve a stable octet, it loses 2 valence electrons to form a magnesium cation ($\text{Mg}^{2+}$): $$\text{Mg} \rightarrow \text{Mg}^{2+} + 2e^-$$

2. Chlorine atom:

   • Atomic number = 17
   • Electronic configuration = 2, 8, 7
   • It needs 1 electron to complete its octet and form a chloride anion ($\text{Cl}^-$): $$\text{Cl} + e^- \rightarrow \text{Cl}^-$$

3. Electron Transfer Process:

   • One magnesium atom transfers its 2 valence electrons to two individual chlorine atoms (1 electron to each chlorine atom). $$\text{Mg} + 2\cdot\ddot{\text{Cl}}: \rightarrow \text{Mg}^{2+} \left[ :\ddot{\text{Cl}}:\right]^-_2$$
   • The strong electrostatic force of attraction holds the oppositely charged ions ($\text{Mg}^{2+}$ and $\text{Cl}^-$) together, forming the ionic compound $\text{MgCl}_2$.

Properties of Ionic Compounds:

1. High Melting and Boiling Points: They have strong inter-ionic electrostatic forces of attraction, requiring a significant amount of heat energy to break the ionic bonds.
2. Electrical Conductivity: They conduct electricity in the molten state or when dissolved in water because free ions are available to move, but they do not conduct electricity in the solid state.