Class 10 Science Metals and Non-metals Notes

Introduction

• Metals: Elements that lose electrons to form cations, usually solid, lustrous, and good conductors of heat and electricity.
• Non-metals: Elements that gain electrons to form anions, usually brittle, dull, and poor conductors.

Physical Properties

Chemical Properties

1. Reaction with Oxygen (Oxidation):
   • Metals → Form basic oxides (Na₂O, MgO)
   • Non-metals → Form acidic oxides (CO₂, SO₂)
2. Reaction with Water:
   • Active metals (Na, K) react vigorously → hydroxides + H₂
   • Non-metals mostly unreactive
3. Reaction with Acids:
   • Metals react with acids → salt + H₂
   • Non-metals generally do not react
4. Reaction with Halogens:
   • Metals → Ionic halides (NaCl)
   • Non-metals → Covalent halides (CCl₄)

Reactivity Series of Metals

• Metals are arranged in order of decreasing reactivity:
  K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Ag > Au
• More reactive metals displace less reactive metals from their compounds.

Alloys

• Definition: Homogeneous mixture of two or more metals (or metal + non-metal)
• Examples:
  • Brass = Copper + Zinc
  • Steel = Iron + Carbon
  • Solder = Lead + Tin
• Purpose: Increase strength, corrosion resistance, hardness

Corrosion and Prevention

• Corrosion: Gradual destruction of metals by chemical reaction with the environment (e.g., rusting of iron).
• Prevention:
  • Painting or coating with oil/grease
  • Galvanization (coating with Zn)
  • Alloying (stainless steel)