78 Iron, for example, is extracted primarily from iron ores, which are rocks and minerals rich in iron oxides. A crystal is any solid material in which the component atoms are arranged in a definite pattern and whose surface regularity reflects its internal symmetry. Can you name any alloys that you are familiar with? Metallic lustre METALS Metals are different from other materials because of their unique atomic structure and bonding properties. These characteristics give metals a distinct set of physical and chemical properties that set them apart from other materials. The majority of metals are found in ores , i.e. rocks containing a sufficient quantity of one or more elements or compounds, but a few such as copper, gold, platinum, and silver frequently occur in the free state because they are chemically inert, meaning they do not easily react with other elements. Structure Metals are usually crystalline solids, meaning they have a crystalline structure in which their atoms are arranged in a regular, repeating pattern. They are elements that very easily form positive ions and that have many electrons that are delocalised (i.e. free to move through the structure), and this allows them to bond easily and form stable compounds (i.e. substances formed when two or more elements are chemically bonded together), and gives them their unique properties. Positive metal ions Layers which can slide over each other alloy: lega to bond: legare copper: rame lustre: lucentezza ore: minerale to polish: lucidare 186 MeCHaNiCs Electrons which can conduct electricity Sea of delocalised electrons Pure metal Alloy Physical, thermal, and electrical features Lustre: metals have a shiny, reflective surface, especially when freshly cut or polished. State: most metals are solid at room temperature, except mercury, which is liquid. Melting and boiling points: metals typically have high melting and boiling points due to strong metallic bonds. Electrical and thermal conductivity: metals are excellent conductors of electricity and heat because of freemoving electrons. Chemical features Reactivity (to other substances): it varies widely among metals. Alkali metals (e.g. sodium, potassium), for example, are highly reactive to substances like water, oxygen, and acids, whereas noble metals (e.g. gold, platinum) are less reactive. Formation of alloys: metals can combine with other metals to form alloys, which often have enhanced properties. Mechanical features Malleability: metals can be hammered or rolled into thin sheets without breaking. Ductility: metals can be stretched into wires. Strength: metals can withstand forces of tension and compression at different levels.