Study Notes: Metals and Non-metals (Class 10)

Overview

Metals and non-metals form the core of material science in Class 10 chemistry. This topic is heavily tested in SOF NSO because it blends physical properties, chemical reactivity and real-world applications like corrosion prevention. Students must be able to differentiate metals from non-metals, predict reaction outcomes using the reactivity series, and explain everyday phenomena like rusting. The topic connects to electrochemistry, periodic table trends and industrial processes. Expect 3–5 direct questions and several integrated problems in the Achievers Section. Master the reactivity series by heart—it's the most frequently tested concept. Physical properties are tested through identification puzzles, while chemical properties appear in reaction-writing and prediction questions.

Key Concepts

• **Physical properties of metals**: Metals are lustrous, malleable, ductile, sonorous and good conductors of heat and electricity. Mercury is the only liquid metal at room temperature. Exceptions exist—sodium and potassium are soft, graphite (non-metal) conducts electricity.

• **Physical properties of non-metals**: Non-metals are dull, brittle (if solid), non-ductile, non-malleable and poor conductors. Iodine is lustrous, diamond is extremely hard—exceptions you must remember.

• **Chemical reactivity**: Metals lose electrons to form positive ions (cations); non-metals gain electrons to form negative ions (anions). The ease of electron loss determines metal reactivity; ease of electron gain determines non-metal reactivity.

• **Reactivity series**: A ranking of metals by decreasing reactivity—potassium is most reactive, gold least. Metals above hydrogen displace H₂ from acids; metals higher in the series displace those below from salt solutions.

• **Displacement reactions**: A more reactive metal displaces a less reactive metal from its salt solution or oxide. Example: zinc displaces copper from copper sulfate.

• **Corrosion**: Slow destruction of metal surfaces by environmental factors—oxygen, moisture, acids. Rusting of iron is the most common example, forming hydrated iron(III) oxide.

• **Ionic compounds**: Metal + non-metal reactions form ionic compounds with high melting points, solubility in water and conductivity in molten/aqueous state due to free-moving ions.

• **Extraction of metals**: Highly reactive metals (Na, K, Ca, Mg, Al) are extracted by electrolysis; moderately reactive metals (Zn, Fe, Pb) by reduction with carbon; least reactive metals (Hg, Cu, Ag, Au) by thermal decomposition or occur free in nature.

Formulas / Key Facts

1. **Reactivity series (decreasing order)**: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt 2. **Reaction with oxygen**: Metal + O₂ → Metal oxide (basic oxide); Non-metal + O₂ → Non-metal oxide (acidic oxide) 3. **Reaction with water**: Highly reactive metal + H₂O → Metal hydroxide + H₂; Less reactive metals react only with steam 4. **Reaction with acids**: Metal + Acid → Salt + H₂ (only metals above H in series) 5. **Displacement**: More reactive metal + Salt of less reactive metal → New salt + Displaced metal 6. **Rusting equation**: 4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O (hydrated iron oxide) 7. **Amphoteric oxides**: Al₂O₃, ZnO react with both acids and bases 8. **Aqua regia**: 3 parts HCl + 1 part HNO₃—dissolves gold and platinum 9. **Ionic bond formation**: Metal atom loses electrons → cation; Non-metal atom gains electrons → anion 10. **Anodizing**: Electrolytic process to thicken protective oxide layer on metals like aluminium

Worked Examples

**Example 1: Displacement Reaction Prediction** *Question*: Will copper displace zinc from zinc sulfate solution? Why? *Solution*: No. According to the reactivity series, zinc (Zn) is more reactive than copper (Cu). Only a more reactive metal can displace a less reactive metal from its salt. Since Cu is below Zn in the series, copper cannot displace zinc from ZnSO₄. The reaction Cu + ZnSO₄ → No reaction.

**Example 2: Identifying Metal from Properties** *Question*: A metal is soft, stored in kerosene, and reacts violently with water producing hydrogen gas. Identify the metal. *Solution*: The metal is sodium (Na) or potassium (K). Both are highly reactive alkali metals stored in kerosene to prevent reaction with atmospheric moisture. They react vigorously with water: 2Na + 2H₂O → 2NaOH + H₂↑ The softness and storage method are key physical clues; violent water reaction confirms high reactivity.

**Example 3: Corrosion Prevention** *Question*: Why does iron rust faster in coastal areas than in deserts? Suggest two prevention methods. *Solution*: Rusting requires both oxygen and moisture. Coastal areas have high humidity (moisture in air) accelerating rust formation. Deserts have very low moisture content, slowing corrosion. Prevention methods: (1) Galvanization—coating iron with zinc which corrodes preferentially; (2) Painting or greasing—creates a barrier blocking oxygen and moisture contact with iron surface.

Common Mistakes

1. **Confusing reactivity series order** → Students mix up middle-order metals like Zn, Fe, Pb. Fix: Remember the mnemonic "Please Send Charlie's Monkeys And Zebras In Lead Harnesses Carrying Heavy Silver Gold Pieces" (P-S-C-M-A-Z-I-L-H-C-H-S-G-P). Also remember K-Na-Ca-Mg-Al is the "electrolysis group."

2. **Thinking all metals react with acids** → Metals below hydrogen (Cu, Ag, Au) do NOT displace H₂ from dilute acids. Fix: Check reactivity series first—only metals above H react with dilute acids to produce H₂ gas.

3. **Assuming physical properties have no exceptions** → Saying "all metals are hard" or "no non-metal conducts electricity." Fix: Always note exceptions—sodium/potassium are soft metals; graphite and iodine are exceptional non-metals (conductive and lustrous respectively).

4. **Writing wrong displacement equations** → Writing Zn + CuSO₄ → ZnSO₄ + Cu but forgetting state symbols or not checking reactivity. Fix: Always verify the displacing metal is higher in the series. Write complete equations with states: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s).

5. **Confusing oxidation and reduction** → In displacement reactions, students mix up which metal is oxidized. Fix: Remember—the more reactive metal loses electrons (oxidized), the less reactive metal ion gains electrons (reduced). In Zn + CuSO₄, zinc is oxidized (Zn → Zn²⁺), copper is reduced (Cu²⁺ → Cu).

Quick Reference

• **Reactivity series top 5**: K, Na, Ca, Mg, Al (extracted by electrolysis)
• **Metals above H in series**: React with dilute acids to give H₂ gas
• **Rust formula**: Fe₂O₃·xH₂O (hydrated iron oxide—needs O₂ + H₂O)
• **Amphoteric oxides**: ZnO, Al₂O₃ (react with both acids and bases)
• **Displacement rule**: Higher in series displaces lower from salt solutions
• **Physical property exceptions**: Na/K soft; Hg liquid; graphite conducts; iodine lustrous; diamond hard