So an atom e.g. Mg (g) -> Fe 3 0 2 caffeine) • Very large molecules (plastics, proteins) • ‘Giant’ molecules (infinite assemblies of atoms) including diamond (C atoms), Silica (Si and O atoms, 1:2) and Carborundum (Si and O atoms, 1:2) and Carborundum (Si and C atoms, 1:1). 8.4 Giant Covalent structures and their free days varied according to these rules: 180° repulsions < 90° repulsions. Remember: lone pairs 82 7.6 Distorted shapes.