Final answer:
Potassium bromide is an ionic compound with a crystalline lattice, iodine is a diatomic molecule, graphite has a layered structure with carbon atoms arranged in a hexagonal lattice, and calcium carbonate is an ionic crystal lattice.
Step-by-step explanation:
Each of the compounds listed has a unique chemical structure:
Potassium bromide (KBr) - This is an ionic compound composed of potassium ions (K+) and bromide ions (Br-). Its structure is a crystalline lattice where each potassium ion is surrounded by six bromide ions and vice versa.
Iodine (I2) - Iodine commonly exists in a molecular form as diatomic molecules, and it has a simple molecular structure where two iodine atoms are bonded together covalently.
Graphite (C) - Graphite has a layered structure with each layer consisting of carbon atoms arranged in a hexagonal lattice. The layers are held together by weak van der Waals forces, allowing them to slide over each other, which gives graphite its lubricating properties.
Calcium carbonate (CaCO3) - This compound has an ionic crystal lattice comprising calcium ions and carbonate ions (CO3^2-). The geometric arrangement of these ions leads to its typical crystal shapes, which include forms like calcite and aragonite in nature.