Ans: Gold is the most malleable metal.

Ans: Sodium is highly reactive. It reacts vigorously with both air and water and can catch fire. To prevent this, it is kept in kerosene.

Ans: Graphite is a non-metal (an allotrope of carbon) that is a good conductor of electricity.

Ans: Graphite (a form of carbon) is a good conductor of electricity.

Ans: The activity series ranks metals from most reactive (K) to least reactive (Au). A metal higher in the series displaces one lower from its salt solution. It helps predict which displacement reactions will occur and guides extraction methods.

Ans: Amphoteric oxides are metal oxides that react with both acids and bases to produce salt and water. Examples: Aluminium oxide (Al₂O₃) and Zinc oxide (ZnO).

Ans: High reactivity (Na, K, Ca, Al): extracted by electrolytic reduction. Moderate reactivity (Zn, Fe, Pb): extracted by reduction with carbon/coke at high temperature. Low reactivity (Ag, Au, Pt): found free in nature; extracted by physical methods. Refining is done by electrolysis for purity.

Ans: The reaction of iron oxide with aluminium is called the thermite reaction: Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + Heat. It is used to join railway tracks or cracked machine parts.

Ans: Steps: (1) Roasting: 2ZnS + 3O₂ → 2ZnO + 2SO₂. (2) Reduction: ZnO + C → Zn + CO. (3) Refining: The crude zinc is then purified by electrolytic refining.

Ans: The reactivity series (electrochemical series) is a list of metals arranged in decreasing order of their reactivity: K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > H > Cu > Hg > Ag > Au. Uses: (1) Predicting displacement reactions: A metal can displace only those metals that are below it in the reactivity series from their salt solutions. Example: Fe + CuSO₄ → FeSO₄ + Cu (Fe above Cu). Zn + FeSO₄ → ZnSO₄ + Fe (Zn above Fe). Cu + ZnSO₄ → No reaction (Cu is below Zn). (2) Extraction of metals: Metals at the top (K, Na, Ca, Mg, Al) are extracted by electrolysis (too reactive for chemical reduction). Metals in the middle (Zn, Fe, Sn, Pb) are extracted by reduction with carbon/CO or other reducing agents. Metals at the bottom (Cu, Hg, Ag, Au) occur naturally as free elements or are easily extracted by roasting.

Ans: An ionic bond is formed by the complete transfer of one or more electrons from a metal atom to a non-metal atom, resulting in oppositely charged ions that are held together by electrostatic attraction. NaCl: Na (2,8,1) loses 1 electron → Na⁺ (2,8) [noble gas config]. Cl (2,8,7) gains 1 electron → Cl⁻ (2,8,8). Na⁺ + Cl⁻ → NaCl (ionic bond). MgO: Mg (2,8,2) loses 2 electrons → Mg²⁺ (2,8). O (2,6) gains 2 electrons → O²⁻ (2,8). Mg²⁺ + O²⁻ → MgO. Properties of ionic compounds: High melting points; conduct electricity in molten state or aqueous solution; generally soluble in water; exist as crystalline solids.

Ans: Mercury is the liquid metal and bromine is the liquid non-metal at room temperature.

Ans: An alloy is a homogeneous mixture of two or more metals, or of a metal with a non-metal. Example: brass (copper and zinc).

Ans: Sodium and potassium (lithium is also soft enough to be cut with a knife).

Ans: In the solid state, ions are held tightly in the crystal lattice by strong electrostatic forces and cannot move. In the molten state (or in solution) the forces are overcome and ions become free to move, so they carry current.

Ans: Aluminium forms a thin, tough layer of aluminium oxide (Al₂O₃) on its surface that protects the metal from further oxidation. Anodising is a process of making this oxide layer thicker by oxidising the aluminium electrolytically in dilute sulphuric acid, so that it can be dyed to give attractive finishes and resists corrosion better.

Ans: Roasting: strong heating of a sulphide ore in excess of air to convert it into oxide, e.g. 2ZnS + 3O₂ → 2ZnO + 2SO₂. Calcination: strong heating of a carbonate ore in limited or no air to convert it into oxide, e.g. ZnCO₃ → ZnO + CO₂. In roasting, sulphur dioxide is released, while in calcination carbon dioxide is released.

Ans: (1) They are solid and hard, brittle crystals. (2) They have high melting and boiling points because of strong electrostatic forces. (3) They are generally soluble in water and insoluble in solvents such as kerosene and petrol. (4) They conduct electricity in molten state and in aqueous solution but not in solid state. (5) They are formed by transfer of electrons between a metal and a non-metal.

Ans: (a) Oxygen: metals form metal oxides, e.g. 2Mg + O₂ → 2MgO; Na and K catch fire so are kept in kerosene; Cu forms black CuO on heating. (b) Water: 2Na + 2H₂O → 2NaOH + H₂ (cold water); 3Fe + 4H₂O → Fe₃O₄ + 4H₂ (steam). (c) Dilute acids: Zn + 2HCl → ZnCl₂ + H₂; copper does not react. (d) Salt solutions: a more reactive metal displaces a less reactive one: Fe + CuSO₄ → FeSO₄ + Cu.

Ans: Metals high in the reactivity series are extracted by electrolytic reduction of their molten chlorides or oxides. For sodium, molten NaCl is electrolysed: at the cathode Na⁺ + e⁻ → Na, and at the anode 2Cl⁻ → Cl₂ + 2e⁻. For aluminium, alumina (Al₂O₃) dissolved in molten cryolite is electrolysed; aluminium collects at the cathode and oxygen at the carbon anode. Carbon cannot be used because these metals have a stronger affinity for oxygen than carbon does, so carbon cannot take oxygen away from their oxides.