Chemistry — Metals and Non-Metals

Overview

Metals and Non-Metals is a foundational chemistry topic for KAR TET Paper II, bridging physical science concepts with everyday applications. This topic tests your understanding of how elements behave based on their electronic configuration and position in the periodic table. Questions typically appear in both content-based MCQs (identifying properties, reactions, uses) and pedagogy-linked items (how to teach these concepts effectively to Classes VI–VIII students).

Mastery requires knowing the characteristic physical and chemical properties of both categories, the reactivity series of metals, and common extraction/reaction patterns. Since upper-primary science emphasises connecting classroom learning to daily life, expect questions linking metals/non-metals to household items, tools, electrical wiring, and biological systems.

Key Concepts

• **Metals** are elements that lose electrons to form positive ions (cations); they are typically lustrous, malleable, ductile, and good conductors of heat and electricity. Examples: iron, copper, aluminium, gold.

• **Non-metals** gain or share electrons to form negative ions (anions) or covalent bonds; they are generally brittle, dull, and poor conductors. Examples: sulphur, carbon, oxygen, nitrogen.

• **Metalloids** (boron, silicon, germanium) show intermediate properties and are used as semiconductors—important for linking to technology in classrooms.

• **Reactivity series** ranks metals by their tendency to lose electrons: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Ag > Au > Pt (most to least reactive).

• **Displacement reactions** occur when a more reactive metal displaces a less reactive metal from its compound. Example: Zn + CuSO₄ → ZnSO₄ + Cu.

• **Ionic compounds** form when metals react with non-metals; these have high melting points, conduct electricity when molten or dissolved, and are generally soluble in water.

• **Corrosion** is the gradual destruction of metals by chemical reaction with the environment (rusting of iron = Fe₂O₃·xH₂O). Prevention methods include painting, oiling, galvanisation, and alloying.

• **Alloys** are homogeneous mixtures of metals (or metal + non-metal) designed to enhance properties—e.g., steel (Fe + C), brass (Cu + Zn), bronze (Cu + Sn).

Formulas / Key Facts

| Concept | Key Fact / Formula | |---------|-------------------| | Reactivity series (top 5) | K, Na, Ca, Mg, Al — react with cold water or steam; stored in kerosene (Na, K) | | Reactivity series (middle) | Zn, Fe, Pb — react with steam; used in galvanisation (Zn) | | Reactivity series (bottom) | Cu, Hg, Ag, Au, Pt — do not react with water or dilute acids; found native | | Reaction with oxygen | Metal + O₂ → Metal oxide (basic); Non-metal + O₂ → Non-metal oxide (acidic) | | Reaction with water | 2Na + 2H₂O → 2NaOH + H₂ (vigorous); Fe + H₂O (steam) → Fe₃O₄ + H₂ | | Reaction with acids | Zn + 2HCl → ZnCl₂ + H₂ (displacement of hydrogen) | | Thermite reaction | 2Al + Fe₂O₃ → Al₂O₃ + 2Fe (highly exothermic; used to weld railway tracks) | | Rusting condition | Iron + Oxygen + Water → Hydrated iron(III) oxide | | Noble metals | Au, Pt — least reactive; resist corrosion; used in jewellery and electronics |