Ionic or Electrovalent Bond
Ionic bonds, as explained through Kössel and Lewis's treatment, fundamentally depend on the formation of positive and negative ions. An ionic bond is formed when an electron is transferred from a metallic atom to a non-metallic atom, resulting in the formation of cations and anions. The processes involved include:
Ion Formation
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Ionization: This is the removal of electrons from a neutral atom, resulting in the formation of a positive ion (cations).
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Example:
For sodium (Na):
M(g) → M+(g) + e–
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Electron Gain: This is the addition of electrons to a neutral atom, forming a negative ion (anions).
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Example:
For chlorine (Cl):
X(g) + e– → X–(g)
Lattice Energy
The ionic bond's strength and the stability of the resulting ionic compounds are significantly influenced by the enthalpy of lattice formation, which is the energy released when gaseous cations and anions come together to form a solid ionic compound.
- Key point: The total energy released in the formation of ionic compounds often compensates for the ionization and electron gain energies, leading to the favorable formation of crystal lattices.
Formation of Ionic Compounds
The interaction between cations and anions creates the crystal lattice structure typical of ionic compounds, where the electrostatic forces of attraction result in a stable arrangement of ions.
- Example: NaCl crystals exhibit a specific crystal structure resulting from the arrangement of Na+ and Cl- ions, which minimizes potential energy and maximizes stability.
Key Factors for Ionic Bond Formation
- The feasibility of forming cations and anions.
- The lattice energy, which represents the stability of the formed ionic solid.
Understanding these principles is crucial, as they enable predictions about reactivity, solubility, and phase changes in various ionic compounds.