Ch-3: Metals and Non-metals 🛠️
1. Physical Properties of Metals
- Metallic Lustre: Metals have a shining surface in their pure state.
- Hardness: Generally hard, but varies (Sodium/Potassium can be cut with a knife!).
- Malleability (आघातवर्ध्यता): Can be beaten into thin sheets (Gold/Silver are best).
- Ductility (तन्यता): Can be drawn into thin wires. (1g Gold $\to$ 2km wire!)
- Conductivity: Best conductors are Silver and Copper. Lead & Mercury are poor.
- Sonority: Produce a ringing sound when struck.
2. Physical Properties of Non-metals
- Exist as Solids (Carbon/Sulphur) or Gases (Oxygen/Hydrogen).
- Bromine is the only liquid non-metal.
- Generally non-lustrous, non-malleable, and poor conductors.
EXCEPTIONS (Exam Favourite!):
• Mercury is liquid at room temp.
• Gallium & Cesium melt on your palm (Very low melting point).
• Iodine is a non-metal but has lustre.
• Graphite (Carbon) is a non-metal but conducts electricity.
• Mercury is liquid at room temp.
• Gallium & Cesium melt on your palm (Very low melting point).
• Iodine is a non-metal but has lustre.
• Graphite (Carbon) is a non-metal but conducts electricity.
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3. Chemical Properties: Reaction with Oxygen
Metal + Oxygen → Metal Oxide (Basic)
- Copper: $2Cu + O_2 \to 2CuO$ (Black oxide).
- Aluminium: $4Al + 3O_2 \to 2Al_2O_3$.
- Amphoteric Oxides (उभयधर्मी ऑक्साइड): Oxides that react with both acids and bases to produce salt and water.
उदाहरण: $Al_2O_3$ और $ZnO$.
4. Reaction with Water (जल के साथ अभिक्रिया)
Metal + Water → Metal Oxide + $H_2$ ↑
Metal Oxide + Water → Metal Hydroxide
Metal Oxide + Water → Metal Hydroxide
- Violent (Cold Water): $Na$ & $K$. $2K(s) + 2H_2O(l) \to 2KOH + H_2 + Heat$.
- Floating: $Ca$ & $Mg$ float because $H_2$ bubbles stick to surface.
- Steam Only: $Al$, $Fe$, $Zn$.
$3Fe(s) + 4H_2O(g) \to Fe_3O_4(s) + 4H_2(g)$. - No Reaction: $Pb, Cu, Ag, Au$.
Fig: Metal reacting with Steam
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5. Reaction with Acids
Metal + Dilute Acid → Salt + $H_2$ ↑
- Nitric Acid ($HNO_3$): $H_2$ gas is NOT evolved because $HNO_3$ is a strong oxidising agent. It oxidises $H_2$ to $H_2O$.
Exception: $Mg$ and $Mn$ react with very dilute $HNO_3$ to give $H_2$. - Aqua Regia (Royal Water): Freshly prepared mixture of Conc. $HCl$ and Conc. $HNO_3$ in 3 : 1 ratio. Can dissolve Gold!
6. Reactivity Series (सक्रियता श्रेणी)
धातुओं की क्रियाशीलता का घटता हुआ क्रम:
Most Reactive
K (Potassium)
Na (Sodium)
Ca (Calcium)
Mg (Magnesium)
Least Reactive
Cu (Copper)
Hg (Mercury)
Ag (Silver)
Au (Gold)
Displacement: A more reactive metal displaces a less reactive one.
$Fe(s) + CuSO_4(aq) \to FeSO_4(aq) + Cu(s)$.
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7. Metals + Non-metals (Ionic Bonding)
- Metals lose electrons (Cations +), Non-metals gain electrons (Anions -).
- The strong electrostatic force of attraction forms Ionic Compounds.
Formation of $MgCl_2$
Mg (2,8,2)
→
$Mg^{2+}$ + $2e^-$
$Mg^{2+}$ + 2[:Cl:]⁻ $\to$ $MgCl_2$
8. Properties of Ionic Compounds
- Physical Nature: Solid and hard; brittle (break into pieces when pressure applied).
- Melting & Boiling Points: Very High! Because large amount of energy is needed to break the strong inter-ionic attraction.
- Solubility: Generally soluble in water, insoluble in kerosene/petrol.
- Conduction: Conduct electricity in Molten state or Aqueous solution (due to free ions). Do not conduct in solid state.
Why high M.P.?
In NaCl, each $Na^+$ is surrounded by $Cl^-$ in a crystal lattice. To overcome these strong electrostatic forces, we need high thermal energy.
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9. Occurrence & Extraction (धातुओं की प्राप्ति)
- Minerals: Naturally occurring elements/compounds in earth’s crust.
- Ores: Minerals with high % of a particular metal that can be extracted profitably.
- Gangue: Impurities (soil, sand) present in ores.
Roasting (Presence of Air) $\to$ Sulphide Ores
Calcination (Limited Air) $\to$ Carbonate Ores
Calcination (Limited Air) $\to$ Carbonate Ores
10. Corrosion (संक्षारण)
- Silver: Turns black (Formation of $Ag_2S$ with $H_2S$ in air).
- Copper: Green coating ($CuCO_3 \cdot Cu(OH)_2$ due to moist $CO_2$).
- Iron: Brown flaky substance called Rust (Needs both Air + Moisture).
11. Prevention of Corrosion
- Painting, Oiling, Greasing.
- Galvanisation: Coating iron/steel with a thin layer of Zinc.
- Alloying: Mixing a metal with other metals/non-metals.
• Stainless Steel: $Fe + Ni + Cr$.
• Brass: $Cu + Zn$ | Bronze: $Cu + Sn$.
• Amalgam: Any alloy where one metal is Mercury.
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