Ionic Compounds

Ionic bonding involves a metal atom transferring electrons to a non-metal atom, forming oppositely charged ions that attract each other. In reality, ionic compounds consist of many alternating positive and negative ions, forming three-dimensional regular lattice structures. These can be represented by diagrams using different colored spheres for ions or by ball and stick models showing the ionic bonds.

Ionic compounds possess very high melting and boiling points due to the numerous strong ionic bonds requiring significant energy to break. They can conduct electricity, but only when melted or dissolved in water. In solid form, ions are fixed and cannot move, but when molten or in solution, ions are free to move, allowing for electrical conductivity.

The formula of an ionic compound is determined by balancing the charges of the constituent ions to achieve overall neutrality. For example, sodium chloride (Na⁺ and Cl⁻) forms NaCl. For magnesium chloride (Mg²⁺ and Cl⁻), two chloride ions are needed, resulting in MgCl₂. More complex compounds like calcium hydroxide (Ca²⁺ and OH⁻) require brackets around polyatomic ions, yielding Ca(OH)₂. For aluminum sulfate (Al³⁺ and SO₄²⁻), the lowest common multiple of the charges is found (6), leading to Al₂(SO₄)₃.

Some common polyatomic ions that are important to memorize include nitrate (NO₃⁻), carbonate (CO₃²⁻), and ammonium (NH₄⁺). Knowing these formulas and their charges simplifies determining the formulas of more complex ionic compounds.