Metals are fundamental elements in chemistry, known for their reactivity, conductivity, and ability to form compounds. Their chemical properties define how they interact with other substances, including oxygen, water, acids, and salts. Understanding these properties is crucial for applications in industry, medicine, and environmental science.
Reaction of Metals with Oxygen
Metals react with oxygen to form metal oxides, which can be basic, amphoteric, or acidic depending on the metal.
General Reaction: Metal + Oxygen → Metal Oxide
Types of Metal Oxides
- Basic Oxides: Formed by highly reactive metals like sodium, potassium, calcium, and magnesium. These oxides dissolve in water to form alkaline solutions.
- Amphoteric Oxides: Formed by metals like aluminium and zinc, which react with both acids and bases.
- Acidic Oxides: Found in metals with lower reactivity, such as chromium and manganese, which behave like non-metal oxides.
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Examples of Metal Oxide Formation
- 4Na + O₂ → 2Na₂O (Sodium Oxide)
- 2Mg + O₂ → 2MgO (Magnesium Oxide)
- 2Al + 3O₂ → 2Al₂O₃ (Aluminium Oxide)
Key Observations:
- Highly reactive metals react at room temperature.
- Moderately reactive metals require heating.
- Least reactive metals (gold, silver) do not react easily with oxygen.
Reaction of Metals with Water
Metals react with water to form metal hydroxides and hydrogen gas. The intensity of the reaction depends on the metal’s position in the reactivity series.
- General Reaction: Metal + Water → Metal Hydroxide + Hydrogen
Reactivity of Metals with Water
- Highly Reactive Metals (Sodium, Potassium, Calcium): React violently with water, producing heat and hydrogen gas.
- Moderately Reactive Metals (Magnesium, Aluminium, Zinc): React slowly with water but more actively with steam.
- Least Reactive Metals (Iron, Copper, Gold): Do not react with cold water but may react with steam.
Examples of Metal-Water Reactions
- 2Na + 2H₂O → 2NaOH + H₂ (Sodium Hydroxide + Hydrogen)
- Ca + 2H₂O → Ca(OH)₂ + H₂ (Calcium Hydroxide + Hydrogen)
- Fe + H₂O (Steam) → Fe₃O₄ + H₂ (Iron Oxide + Hydrogen)
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Key Observations:
- Alkali metals react explosively with water.
- Transition metals react only with steam.
- Noble metals (gold, platinum) do not react with water.
Reaction of Metals with Acids
Metals react with dilute acids to form metal salts and hydrogen gas. The reaction depends on the metal’s position in the reactivity series.
- General Reaction: Metal + Acid → Metal Salt + Hydrogen
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Reactivity of Metals with Acids
- Highly Reactive Metals (Sodium, Potassium, Calcium): React explosively with acids.
- Moderately Reactive Metals (Magnesium, Zinc, Iron): React steadily with acids.
- Least Reactive Metals (Copper, Silver, Gold): Do not react with acids.
Examples of Metal-Acid Reactions
- Zn + H₂SO₄ → ZnSO₄ + H₂ (Zinc Sulfate + Hydrogen)
- Mg + 2HCl → MgCl₂ + H₂ (Magnesium Chloride + Hydrogen)
- Fe + 2HCl → FeCl₂ + H₂ (Iron Chloride + Hydrogen)
Key Observations:
- Metals above hydrogen in the reactivity series react with acids.
- Metals below hydrogen (copper, silver, gold) do not react with acids.
Reaction of Metals with Other Metal Salts
More reactive metals can displace less reactive metals from their compounds in a displacement reaction.
General Reaction: More Reactive Metal + Metal Salt → New Metal + New Salt
Examples of Metal Displacement Reactions
- Zn + CuSO₄ → ZnSO₄ + Cu (Zinc displaces Copper)
- Fe + Pb(NO₃)₂ → Fe(NO₃)₂ + Pb (Iron displaces Lead)
Key Observations:
- Metals higher in the reactivity series replace lower metals.
- Used in metal extraction and purification processes.
Frequently Asked Questions (FAQ) – Chemical Properties of Metals
Why do metals react with oxygen?
Metals donate electrons to oxygen, forming metal oxides.
Which metals react violently with water?
Sodium and potassium react explosively with water, producing hydrogen gas.
Why do some metals not react with acids?
Copper, silver, and gold are less reactive and do not displace hydrogen from acids.
What is an amphoteric oxide?
An oxide that reacts with both acids and bases, like Al₂O₃ (Aluminium Oxide).
How does the reactivity series affect metal reactions?
Highly reactive metals react faster, while less reactive metals show minimal or no reaction.
What happens when metals react with steam?
Iron reacts with steam to form iron oxide and hydrogen gas.
Why do metals conduct electricity?
Metals have free-moving electrons, allowing them to conduct electricity efficiently.
Can metals react with bases?
Some metals, like aluminium and zinc, react with bases to form complex salts.
What is the role of displacement reactions in metal extraction?
More reactive metals replace less reactive metals in compounds, aiding in metal purification.
How do metals react with chlorine?
Metals react with chlorine to form metal chlorides, like NaCl (Sodium Chloride).
Conclusion
Metals exhibit unique chemical properties, reacting with oxygen, water, acids, and salts based on their reactivity series. Understanding these reactions helps in industrial applications, metal extraction, and daily chemistry.
