Metals and Non-Metals
1. Physical Properties of Metals
Metals are typically characterized by their luster, malleability, ductility, and conductivity. They are generally solid at room temperature (except for mercury, which is liquid) and have a shiny appearance.
Example: Gold is a metal known for its luster and malleability. It can be hammered into thin sheets (gold leaf) and drawn into wires.
2. Chemical Properties of Metals
Metals tend to lose electrons and form positive ions (cations). They react with non-metals to form ionic compounds and with acids to produce hydrogen gas.
Example: Sodium (a metal) reacts with chlorine (a non-metal) to form sodium chloride (table salt): \( 2Na + Cl_2 \rightarrow 2NaCl \).
3. Occurrence of Metals
Metals are found in the Earth's crust, often in the form of ores. They are extracted through processes like mining and refining.
Example: Iron is extracted from its ore, hematite (Fe₂O₃), through a process called smelting.
4. Physical Properties of Non-Metals
Non-metals are generally brittle, lack luster, and are poor conductors of heat and electricity. They can be solid, liquid, or gas at room temperature.
Example: Sulfur is a non-metal that is brittle and yellow in color. It does not conduct electricity and is a poor thermal conductor.
5. Chemical Properties of Non-Metals
Non-metals tend to gain electrons and form negative ions (anions). They react with metals to form ionic compounds and with other non-metals to form covalent compounds.
Example: Chlorine (a non-metal) reacts with hydrogen (another non-metal) to form hydrogen chloride (HCl), a covalent compound.
6. Occurrence of Non-Metals
Non-metals are abundant in the Earth's atmosphere and crust. They are often found in elemental form or as compounds.
Example: Oxygen is the most abundant non-metal in the Earth's atmosphere, making up about 21% of the air we breathe.
7. Metalloids
Metalloids, also known as semimetals, have properties of both metals and non-metals. They are typically brittle, have a moderate conductivity, and are used in semiconductors.
Example: Silicon is a metalloid used in the production of computer chips due to its semiconducting properties.
8. Alloys
Alloys are mixtures of two or more metals or a metal and a non-metal. They often have improved properties compared to pure metals, such as increased strength or corrosion resistance.
Example: Steel is an alloy of iron and carbon, which is stronger and more resistant to corrosion than pure iron.
9. Corrosion and Rusting
Corrosion is the degradation of a material due to chemical reactions with its environment. Rusting is a specific form of corrosion that occurs with iron and its alloys.
Example: When iron is exposed to oxygen and moisture, it forms iron oxide, commonly known as rust: \( 4Fe + 3O_2 \rightarrow 2Fe_2O_3 \).