Cation Formation: Metal atoms lose their valence electrons to form positive ions. For example, a Group 2 metal atom will lose two electrons to form a ion, such as .
Anion Formation: Non-metal atoms gain electrons to fill their valence shells, forming negative ions. A Group 17 element will gain one electron to form a ion, such as .
Charge Neutrality: The total positive charge of the cations must exactly balance the total negative charge of the anions in the resulting compound, leading to an overall neutral empirical formula.
Electrostatic Force: The strength of the bond is governed by Coulomb's Law, where the force is proportional to the product of the charges and inversely proportional to the square of the distance between them:
| Feature | Ionic Bonding | Covalent Bonding |
|---|---|---|
| Mechanism | Complete transfer of electrons | Sharing of electron pairs |
| Constituents | Metal and Non-metal | Two or more Non-metals |
| Structure | Giant crystalline lattice | Discrete molecules or giant covalent |
| Forces | Electrostatic attraction between ions | Attraction between nuclei and shared electrons |
Charge Notation: Always write charges with the number first followed by the sign (e.g., or ). Writing is often reserved for oxidation states in advanced chemistry.
Naming Convention: Ensure you change the suffix of the non-metal to '-ide' (e.g., Oxygen becomes Oxide, Sulfur becomes Sulfide) when it forms an anion.
State Symbols: Remember that ionic compounds are almost always solid () at room temperature due to the strength of the lattice. They only conduct electricity in liquid () or aqueous () states.
Predicting Formulas: Use the 'cross-over' method where the numerical value of the charge on one ion becomes the subscript for the other ion to ensure charge balance.
Conductivity Error: A common mistake is stating that ionic solids conduct electricity. They do not, because the ions are locked in fixed positions and cannot move to carry a charge.
Bonding Misconception: Students often think the 'lines' in a ball-and-stick model represent physical bonds. In reality, the bond is a multi-directional electrostatic field acting throughout the lattice.
Solubility Assumption: While many ionic compounds are soluble in water, not all are. Solubility depends on the balance between lattice energy and the hydration energy of the ions.
