Metals and Non-metals

Prerequisites

• Acids, Bases and Salts — metal oxides are basic and non-metal oxides acidic; metals react with acids to release hydrogen.
• Minerals, Energy and Industries (Chhattisgarh) — where the ores discussed here are actually mined in the state.
• Mineral and Energy Resources of India — the national distribution of iron ore, bauxite and copper.

The Hook: From Bailadila Hills to the Bhilai Rail

Why it matters: Prelims P-I asks exceptions (the liquid metal, the non-metal that conducts), ores and their metals, alloys and their components, and corrosion prevention. Chhattisgarh’s mineral wealth makes this a natural bridge to Part 2 (Chhattisgarh) questions and to Mains answers on industry.

Physical Properties: The Rule and the Exceptions

The exceptions examiners ask

Allotropes: diamond, graphite and fullerenes (C-60, buckminsterfullerene) are different forms of the same element, carbon.

Chemical Properties

Oxides: metals basic, non-metals acidic

• Metal + oxygen → metal oxide, which is basic (e.g. Na₂O, MgO, CaO). Soluble ones dissolve to give alkalis.
• Non-metal + oxygen → non-metal oxide, which is acidic (CO₂, SO₂) or neutral (CO, N₂O).
• Amphoteric oxides react with both acids and bases: aluminium oxide (Al₂O₃) and zinc oxide (ZnO).
• Aluminium forms a thin, tough oxide layer that protects it from further corrosion. Anodising thickens this layer deliberately.

Reaction with water

Reaction with acids

Metals above hydrogen in the reactivity series displace hydrogen from dilute HCl and H₂SO₄. Hydrogen is generally not evolved with nitric acid, because HNO₃ is a strong oxidising agent that oxidises the hydrogen to water; magnesium and manganese with very dilute nitric acid are the exceptions.

Aqua regia (अम्लराज) = 3 parts concentrated HCl : 1 part concentrated HNO₃. It dissolves gold and platinum, which no single acid can. The name means “royal water”.

The reactivity series

flowchart LR
    K["K"] --> Na["Na"] --> Ca["Ca"] --> Mg["Mg"] --> Al["Al"] --> Zn["Zn"] --> Fe["Fe"] --> Pb["Pb"] --> H["[H]"] --> Cu["Cu"] --> Hg["Hg"] --> Ag["Ag"] --> Au["Au"]

Most reactive (left) to least reactive (right). A more reactive metal displaces a less reactive one from its salt solution. An iron nail in blue copper sulphate solution turns brown (copper coats it) and the solution turns pale green (iron sulphate). Copper cannot displace iron.

Ionic compounds

Metals lose electrons and non-metals gain them, forming ionic compounds such as NaCl and MgCl₂. These have high melting points, are usually soluble in water, and conduct electricity in molten or dissolved form but not as solids (the ions cannot move).

Occurrence and Extraction (Metallurgy)

• Mineral: a naturally occurring compound containing a metal. Ore: a mineral from which the metal can be extracted profitably. All ores are minerals; not all minerals are ores.
• Gangue: earthy impurities (sand, soil) in the ore, removed before extraction.
• Native metals: gold, silver, platinum and sometimes copper occur free because they are unreactive.

Ores to remember

Extraction depends on reactivity

flowchart TD
    A["Ore (after removing gangue)"] --> B{"Reactivity of the metal"}
    B -->|"High: K, Na, Ca, Mg, Al"| C["Electrolysis of the molten compound
e.g. aluminium from alumina"]
    B -->|"Middle: Zn, Fe, Pb, Cu"| D["Sulphide ore: roasting in air
Carbonate ore: calcination (little air)
Then reduction with carbon (coke)"]
    B -->|"Low: Hg, Cu (some)"| E["Heating the sulphide ore alone
e.g. cinnabar gives mercury"]
    C --> F["Refining
(electrolytic refining for Cu, Zn, Ag, Au)"]
    D --> F
    E --> F

• Roasting = heating a sulphide ore strongly in excess air. Calcination = heating a carbonate ore in limited air. Both give the oxide.
• Aluminium is too reactive to be reduced by carbon. Alumina from bauxite is dissolved in molten cryolite and electrolysed (the Hall–Héroult process). This is why aluminium smelters need cheap, large-scale electricity and sit near coal or hydro power, as BALCO does at Korba.
• Thermit reaction: iron oxide reacted with aluminium powder gives molten iron with intense heat; it is used to weld railway tracks and broken machine parts.
• Electrolytic refining: impure metal is the anode, a thin strip of pure metal the cathode; pure metal deposits on the cathode and impurities fall as anode mud.

Corrosion and Its Prevention

Corrosion (संक्षारण) is the slow eating away of a metal by air, moisture and chemicals.

Rusting is faster in humid, coastal and polluted air (salt and acid speed it up).

Prevention methods

Alloys (मिश्रधातु)

An alloy is a homogeneous mixture of a metal with other metals or a non-metal. Alloying usually lowers electrical conductivity and melting point compared with the pure metal and increases hardness and corrosion resistance.

Gold purity: 24 carat = pure gold, too soft for ornaments. 22 carat = 22 parts gold + 2 parts copper or silver (about 91.6% gold). In India, BIS hallmarking of gold jewellery became mandatory in phases from 23 June 2021.

Chhattisgarh Angle: A Metals State

Memory Tricks

Don’t Confuse

Common Mistakes

Practice

All questions below are original practice questions written in CGPSC style. They are not previous-year questions.

Level 1: Foundation

1. The only metal that is liquid at room temperature is ______; the only non-metal that is liquid is ______.
2. Coating iron with zinc to prevent rusting is called ______.
3. Aqua regia is a mixture of concentrated ______ and concentrated ______ in the ratio 3:1.

Level 2: Prelims MCQs

Q1. Consider the following statements:

1. Graphite, a non-metal, is a good conductor of electricity.
2. Sodium is stored under kerosene because it reacts vigorously with air and water.
3. Aluminium oxide reacts with both acids and bases.

Which of the statements given above is/are correct?

• (a) 1 and 2 only
• (b) 2 and 3 only
• (c) 1 and 3 only
• (d) 1, 2 and 3

Q2. Match List I (Alloy) with List II (Main components):

• (a) A-1, B-4, C-2, D-3
• (b) A-4, B-1, C-2, D-3
• (c) A-4, B-1, C-3, D-2
• (d) A-1, B-4, C-3, D-2

Q3. Aluminium is extracted from alumina by electrolysis rather than by reduction with carbon because:

• (a) alumina is not found in nature
• (b) aluminium is placed high in the reactivity series and has a strong affinity for oxygen
• (c) carbon reacts with cryolite
• (d) electrolysis is cheaper than coke

Q4. Which of the following ore–metal pairs is correctly matched?

• (a) Galena – Mercury
• (b) Cinnabar – Lead
• (c) Cassiterite – Tin
• (d) Chalcopyrite – Zinc

Q5. With reference to Chhattisgarh, consider the following statements:

1. Chhattisgarh is the only state in India that produces tin concentrates.
2. BALCO at Korba was set up as a private company and later nationalised.
3. The Katghora block auctioned for exploration is associated with lithium.

Which of the statements given above is/are correct?

• (a) 1 and 3 only
• (b) 2 only
• (c) 1 and 2 only
• (d) 1, 2 and 3

Level 3: Mains Answer Writing

Q1. (60 words) What is corrosion? Explain two methods of preventing the rusting of iron.

Q2. (150–200 words) Explain, with reference to chemistry, why Chhattisgarh has emerged as an important centre of steel and aluminium production. Mention the environmental challenges involved.

Quick Revision Table

Key Takeaways

What’s Next

• Soaps, Medicines and Food Chemicals — chemistry in the home and the clinic
• Common Chemicals and Materials — cement, glass, plastics, fertilisers and fuels
• Minerals, Energy and Industries (Chhattisgarh) — the state’s mineral map in detail
• Industrial Policy and MSMEs — disinvestment and the metals sector