Chap#1 topic#5 2nd year, Oxides of period 3 elements

The behavior of Period 3 oxides provides one of the clearest demonstrations of periodic trends in chemistry. As you move across the third period from sodium to chlorine, elements transition from metals to metalloids to non-metals, and their highest oxides undergo a simultaneous shift from ionic to covalent, and from strongly basic to strongly acidic. Physical Properties and Structure Ionic Oxides (\text{Na}_2\text{O}, \text{MgO}): High melting and boiling points due to strong electrostatic forces between oppositely charged ions (\text{Na}^+, \text{Mg}^{2+}, and \text{O}^{2-}). They exist as giant ionic lattices. Borderline Oxide (\text{Al}_2\text{O}_3): Possesses significant covalent character because the high charge density of the \text{Al}^{3+} ion polarizes the oxygen anion. Giant Covalent Oxide (\text{SiO}_2): Silicon dioxide forms a macromolecular 3D network structure, resulting in an exceptionally high melting point. Simple Molecular Oxides (\text{P}_4\text{O}_{10}, \text{SO}_3, \text{Cl}_2\text{O}_7): Covalent molecules held together by weak intermolecular van der Waals forces, resulting in much lower melting and boiling points (many exist as gases or volatile liquids at room temperature).