Chapter 3: Metals and Non-metals

Introduction

• Metals: Shiny, good conductors of heat and electricity, malleable, and ductile. Found on the left side of the periodic table.
• Non-metals: Usually dull, poor conductors, brittle. Found on the right side of the periodic table.
• Metalloids: Elements with properties intermediate between metals and non-metals (e.g., Silicon, Germanium).

Physical Properties

Metals:

• Luster: They have a shiny appearance.
• Malleability: Can be beaten into sheets.
• Ductility: Can be drawn into wires.
• Conductivity: Good conductors of heat and electricity.
• Sonorous: Produce a ringing sound when struck.

Non-metals:

• Lack of Luster: Mostly dull or non-shiny.
• Brittle: Not malleable or ductile; if solid, they break easily.
• Poor Conductors: Bad conductors of heat and electricity (except graphite).
• Non-sonorous: Do not produce a ringing sound when hit.

Chemical Properties

Reactivity with Oxygen:

• Metals: Form oxides, which are basic or amphoteric. Examples:
  • 4Na+O₂→2Na₂O
  • 2Mg+O₂→2MgO
• Non-metals: Form oxides, which are acidic or neutral. Example:
  • S+O₂→SO₂

Reactivity with Water:

• Metals: Some react with water to form hydroxides and hydrogen gas:
  • 2Na+2H₂O→2NaOH+H₂
  • Magnesium reacts with steam:
• Non-metals: Generally do not react with water at room temperature.

Mg+H₂O→MgO+H₂

Reactivity with Acids:

• Metals: React with dilute acids to produce salts and hydrogen gas:
  • Zn+2HCl→ZnCl₂+H₂
• Non-metals: Most do not react with acids.

Reactivity with Bases:

• Metals: Some metals like aluminum react with bases to form aluminates and hydrogen:
  • 2Al+2NaOH+6H₂O→2NaAl(OH)₄+3H₂
• Non-metals: Typically do not react with bases.

Reactivity Series

• Order: Arranges metals in order of their reactivity from most reactive to least (e.g., Potassium > Sodium > Calcium > Magnesium > Aluminum > Zinc > Iron > Lead > Copper > Silver > Gold).
• Uses: Helps predict displacement reactions where a more reactive metal displaces a less reactive one from its salt solution.

Formation of Ionic Compounds

• Metals and Non-metals: When a metal reacts with a non-metal, they form ionic compounds:
  • Example: Sodium (Na) + Chlorine (Cl) → Sodium Chloride (NaCl).

Occurrence of Metals

• Native: Some metals like gold occur in their free state.
• Compounds: Most metals occur in the earth's crust as oxides, sulfides, carbonates, etc.
• Extraction:
  • Ores: Rocks from which metals can be economically extracted.
  • Enrichment: Concentration of ore through various methods like froth floatation, magnetic separation.
  • Extraction: Using methods like reduction, electrolysis depending on the reactivity of the metal.

Corrosion

• Definition: Gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment.
• Types:
  • Rusting: Specific to iron; requires oxygen and moisture.
  • Tarnish: Formation of a thin layer of oxides on metals like silver or copper.

4Fe+3O₂+6H₂O→4Fe(OH)₃

Prevention of Corrosion:

• Galvanization (coating with zinc), painting, alloying, cathodic protection.

Alloys

• Definition: Mixture of a metal with other elements, often used to improve properties like strength, corrosion resistance.
• Common Alloys:
  • Brass: Copper + Zinc
  • Bronze: Copper + Tin
  • Steel: Iron + Carbon (with various other elements for different types like stainless steel)

Uses of Metals and Non-metals

Metals:

• Construction (Iron, Steel), Electrical wiring (Copper), Vehicles (Aluminum, Steel), Coins (Nickel, Copper).

Non-metals:

• Oxygen for breathing, Nitrogen in fertilizers, Chlorine for water purification, Carbon in various forms (diamond, graphite, coal).

Environmental Impact

• Mining: Leads to deforestation, soil erosion, water pollution.
• Corrosion: Economic loss but also release of harmful substances into the environment.
• Recycling: Important to reduce environmental impact, conserve resources.

Conclusion

• Understanding the properties and reactions of metals and non-metals is crucial for technological advancements, environmental protection, and daily life applications.