Metals and Non-metals: Properties, Reactions, and Extraction
Metals and non-metals are fundamental elements distinguished by their physical characteristics, such as luster, hardness, and conductivity, and their chemical reactivity with substances like air, water, and acids. Understanding these differences is crucial for predicting their behavior, especially in forming ionic compounds and determining the appropriate methods for metal extraction and corrosion prevention based on their position in the reactivity series.
Key Takeaways
Metals are generally hard, lustrous, malleable, and good conductors of heat and electricity.
Chemical reactivity determines extraction methods and displacement reactions in solutions.
Ionic compounds form via electron transfer, resulting in high melting points and water solubility.
Metallurgy involves concentrating ores, converting them to oxides, and reducing them to pure metal.
Corrosion, like rusting, requires both oxygen and water and can be prevented by coating methods.
What are the key physical properties that distinguish metals from non-metals?
Metals and non-metals exhibit distinct physical properties that allow for easy classification. Metals typically possess a shining surface (luster), are generally hard, and exist as solids at room temperature, except for mercury. Conversely, non-metals are usually dull, soft (except diamond), and can exist as solids, liquids (bromine), or gases. These differences also extend to mechanical properties, where metals are malleable and ductile, while non-metals are brittle, making them non-malleable and non-ductile.
- Metals:
- Lustre: Possess a shining surface.
- Hardness: Generally hard (Except Na, K, Li).
- Malleability/Ductility: Can be beaten into sheets or drawn into wires.
- Conductivity: Good conductors of heat and electricity.
- Sonority: Produce sound on striking.
- State: Solid at room temp (Except Mercury).
- Non-Metals:
- Lustre: Dull (Except Iodine).
- Hardness: Generally soft (Except Diamond).
- Malleability/Ductility: Brittle (Non-malleable, Non-ductile).
- Conductivity: Poor conductors (Except Graphite).
- Sonority: Non-sonorous.
- State: Solids or Gases (Except Bromine - liquid).
How do metals react chemically with air, water, and acids?
Metals demonstrate varied chemical reactivity depending on the substance they interact with, which is a key indicator of their position in the reactivity series. When reacting with air (oxygen), metals form metal oxides, which are generally basic, although some, like aluminum and zinc oxides, are amphoteric, reacting with both acids and bases. Reactions with water range from vigorous (Na, K) to requiring steam (Al, Zn, Fe), while reactions with dilute acids typically produce a salt and hydrogen gas, unless the acid is a strong oxidizing agent like nitric acid.
- Reaction with Air (Oxygen): Forms Metal Oxides (Generally Basic).
- Amphoteric Oxides (Al₂O₃, ZnO): React with both acids and bases.
- Reaction with Water: Metal + Water → Metal Oxide/Hydroxide + H₂.
- Reactivity Levels: Vigorous with cold water (Na, K, Ca); reacts only with steam (Al, Zn, Fe); no reaction (Pb, Cu, Ag, Au).
- Reaction with Acids (Dilute): Metal + Dilute Acid → Salt + H₂ Gas.
- Displacement Reaction: More reactive metal displaces less reactive metal from its salt solution (e.g., Fe + CuSO₄ → FeSO₄ + Cu).
What is the Reactivity Series and why is it significant in chemistry?
The Reactivity Series is a fundamental chemical tool defined as a list of metals arranged in order of decreasing reactivity, starting with potassium (K) and ending with gold (Au). This arrangement is highly significant because it allows chemists to predict the outcome of various chemical reactions, particularly displacement reactions. A metal higher up in the series can displace any metal below it from its salt solution, providing a clear framework for understanding relative chemical behavior and stability.
- Definition: List of metals arranged in order of decreasing reactivity.
- Order (K to Au): K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au.
- Significance: Predicts displacement reactions.
How are ionic compounds formed and what are their characteristic properties?
Ionic compounds are formed through the complete transfer of electrons from a metal atom to a non-metal atom. The metal loses electrons to become a positively charged cation, while the non-metal gains electrons to become a negatively charged anion. These oppositely charged ions are then held together by strong electrostatic forces, forming a stable ionic bond. Due to this strong bonding, ionic compounds exhibit high melting and boiling points, are typically solid, hard, and brittle, and conduct electricity only when molten or dissolved in water.
- Formation: Transfer of electrons from metal to non-metal.
- Ion Formation: Metal loses electrons → Cation (+); Non-metal gains electrons → Anion (-).
- Bonding: Held by strong electrostatic forces.
- Physical Nature: Solid, hard, brittle.
- Melting & Boiling Point: High.
- Solubility: Generally soluble in water; insoluble in petrol/kerosene.
- Conduction of Electricity: Conducts in molten state or solution, not solid state.
What are the key steps in metallurgy for extracting metals based on their reactivity?
Metallurgy involves extracting metals from their naturally occurring minerals, known as ores, after separating them from earthly impurities called gangue. The extraction process varies significantly based on the metal's reactivity. Highly reactive metals (K, Na, Ca) require electrolytic reduction of their molten ores, as carbon cannot reduce them. Medium reactive metals (Zn, Fe) are first converted to oxides via roasting (sulphides) or calcination (carbonates), followed by reduction using carbon. Low reactive metals (Ag, Au) are often found in a free state or extracted simply by roasting their sulphide ores.
- Basic Terms:
- Minerals: Natural elements/compounds in earth's crust.
- Ores: Minerals from which metal can be profitably extracted.
- Gangue: Earthly impurities (soil, sand) in an ore.
- Extraction (Low Reactivity - Ag, Au): Found in free state or extracted by Roasting (Heating in air).
- Extraction (Medium Reactivity - Zn, Fe, Pb): Convert to Oxide (Roasting/Calcination), then reduce using Carbon/Coke.
- Extraction (High Reactivity - K, Na, Ca, Mg, Al): Cannot be reduced by Carbon; requires Electrolytic Reduction of molten ores.
- Refining: Electrolytic Refining uses impure metal as the Anode, pure metal strip as the Cathode, and metal salt solution as the Electrolyte.
How does corrosion occur and what methods are used for its prevention?
Corrosion is the natural deterioration of metals resulting from their reaction with the environment, specifically air, moisture, or chemicals. Classic examples include the rusting of iron, which requires both oxygen and water, the tarnishing of silver (forming a black Ag₂S coating), and the green coating of basic copper carbonate on copper. Prevention methods focus on isolating the metal from the corrosive environment. These strategies include barrier methods like painting or greasing, coating methods such as galvanization (zinc coating) or chrome plating, and alloying the metal to enhance its resistance.
- Definition: Deterioration of metals by air, moisture, or chemicals.
- Examples:
- Rusting of Iron: Brown flaky substance; requires both Air (Oxygen) and Water.
- Tarnishing of Silver: Black coating of Ag₂S.
- Corrosion of Copper: Green coating of basic copper carbonate.
- Prevention Methods:
- Barrier Methods: Painting, Oiling, Greasing.
- Coating Methods: Galvanisation (Coating with Zinc), Chrome Plating, Anodising (For Aluminium).
- Alloying: Mixing metal with other metals/non-metals.
Frequently Asked Questions
What are amphoteric oxides?
Amphoteric oxides, such as aluminum oxide (Al₂O₃) and zinc oxide (ZnO), are metal oxides that exhibit dual chemical behavior. They react with both acids and bases to form salt and water, unlike typical metal oxides which are only basic.
Why do ionic compounds only conduct electricity in the molten state or solution?
Ionic compounds are held together by strong electrostatic forces in the solid state, preventing ion movement. When melted or dissolved, the ions become mobile and free to move, allowing the compound to conduct an electric current.
What is the difference between roasting and calcination in metallurgy?
Both are processes to convert ores into metal oxides. Roasting involves heating a sulphide ore strongly in the presence of air. Calcination involves heating a carbonate ore strongly in a limited supply of air or absence of air.
