Metals and Non-metals — Important Questions

Ionic bond

Step 1: Magnesium (metal) has 2 electrons in its outermost shell, while chlorine (non-metal) has 7 electrons. Step 2: Magnesium loses 2 electrons to form Mg²⁺ ion, achieving stable octet configuration. Step 3: Each chlorine atom gains 1 electron to form Cl⁻ ion, also achieving stable octet. Step 4: The oppositely charged ions (Mg²⁺ and Cl⁻) attract each other through electrostatic forces, forming ionic bonds. Step 5: The resulting compound MgCl₂ is an ionic compound with high melting point and conducts electricity in molten state.

Electrolytic reduction

Step 1: Metals high in reactivity series (like sodium, magnesium, calcium, aluminum) have strong affinity for oxygen. Step 2: These metals cannot be extracted by heating with carbon because they have more affinity for oxygen than carbon does. Step 3: Electrolytic reduction uses electrical energy to break strong ionic bonds in molten compounds. Step 4: For example, sodium is extracted by electrolysis of molten NaCl: Na⁺ + e⁻ → Na (at cathode). Step 5: This method provides enough energy to overcome the strong electrostatic forces in highly reactive metal compounds.

Both air and water

Step 1: Rusting is the corrosion of iron in the presence of oxygen and water to form hydrated iron oxide (rust). Step 2: The experiment with three test tubes shows that iron rusts only when both air and water are present. Step 3: In dry air alone (test tube C with anhydrous CaCl₂), iron doesn't rust because water is absent. Step 4: In boiled water with oil layer (test tube B), iron doesn't rust because oxygen is absent. Step 5: Only in normal water exposed to air (test tube A) does rusting occur, proving both conditions are necessary.

Zinc

Step 1: Galvanizing is a process of coating iron or steel with a thin layer of zinc to prevent rusting. Step 2: Zinc is more reactive than iron in the reactivity series, so it acts as a sacrificial metal. Step 3: Even if the zinc coating is scratched, zinc will corrode first instead of iron, protecting the underlying metal. Step 4: Zinc forms a protective oxide layer (ZnO) that adheres well and prevents further corrosion. Step 5: Common galvanized items include buckets, pipes, and roofing sheets that have a shiny, silvery appearance.