Metals, Non-Metals & Alloys

Overview

Metals, non-metals, and alloys form a core area in UPSC General Science — questions appear on physical and chemical properties, the reactivity series, metallurgy, corrosion, and strategic minerals. This topic also links to GS-3 (economy/security) through rare earth elements and India's critical minerals policy.

Properties of Metals vs Non-Metals

Physical Properties

Chemical Properties

Metalloids (Semi-Metals)

Metalloids occupy the diagonal border between metals and non-metals in the periodic table. The commonly recognised metalloids are Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), and Tellurium (Te).

Comparison: Metals vs Non-Metals vs Metalloids

Reactivity Series of Metals

The reactivity series arranges metals in decreasing order of their tendency to lose electrons and react with other substances.

Key principles:

• A more reactive metal can displace a less reactive metal from its salt solution (single displacement reaction).
• Metals above hydrogen in the series react with dilute acids to release H₂ gas; those below hydrogen (Cu, Hg, Ag, Au, Pt) do not.
• The series also determines the extraction method: highly reactive metals (K to Al) require electrolysis; moderately reactive metals (Zn to Pb) are reduced with carbon/coke; low-reactivity metals (Cu, Hg) are obtained by roasting; and the least reactive (Ag, Au, Pt) occur free in nature.

Mnemonic for the reactivity series: King Nathan Came Mighty Along — Zealous Fellow Pb(Lead) Had Cups of Hg(Mercury) with Ag(Silver) and Au(Gold) and Pt(Platinum).

Metallurgy

Metallurgy is the process of extracting metals from their ores and refining them for use.

Common Ore Types

Steps in Metallurgy

Froth flotation — Used for sulphide ores; ore is mixed with water and pine oil; sulphide particles attach to oil-froth and float, while gangue sinks.

Thermite reaction — Fe₂O₃ + 2Al → 2Fe + Al₂O₃ — highly exothermic; used for welding railway tracks.

Electrolytic refining — The impure metal is made the anode, a thin strip of pure metal is the cathode, and acidified salt solution of the metal acts as the electrolyte. On passing current, pure metal deposits on the cathode while impurities settle as anode mud. This method is used for refining copper, zinc, tin, nickel, silver, and gold.

Corrosion and Its Prevention

Corrosion is the gradual destruction of metals by chemical or electrochemical reaction with the environment.

Types of Corrosion

Prevention Methods

Important Alloys

An alloy is a homogeneous mixture of a metal with one or more other metals or non-metals.

Why alloys? Pure metals are often too soft, too reactive, or lack desired properties. Alloying improves hardness, strength, corrosion resistance, or lowers melting point.

India's Major Mineral Resources

Noble Metals

Noble metals are found in free state in nature because they do not react easily with other elements.

Rare Earth Elements (REEs)

Strategic concern: Monazite sands also contain thorium (radioactive), which complicates mining and places it under atomic energy regulations.

Critical Minerals — India's Policy

UPSC Relevance

Prelims focus areas: Properties of metals vs non-metals, reactivity series order, alloy compositions (especially stainless steel, bronze, brass, duralumin), types of corrosion (uniform, galvanic, pitting), corrosion prevention methods, noble metals and aqua regia.

Mains and essay links (GS-3): Rare earth elements and India's strategic vulnerability, critical minerals for energy transition, China's dominance in REE supply chains, KABIL and overseas mineral diplomacy, National Critical Minerals Mission (2025), thorium reserves and India's three-stage nuclear programme.

Key terms to remember: Galvanisation, sacrificial anode, froth flotation, thermite reaction, Hall-Heroult process, aqua regia, monazite sands, anode mud, electrolytic refining, galvanic corrosion, pitting corrosion, stress corrosion cracking.

Common traps in Prelims:

• German silver contains no silver — it is Cu + Zn + Ni.
• Mercury is the only metal that is liquid at room temperature; bromine is a liquid non-metal.
• Graphite (a non-metal) conducts electricity — it is the key exception.
• Diamond has the highest hardness (10 on Mohs scale) among natural substances but is a poor conductor of electricity.
• Stainless steel contains chromium (minimum 10.5%), which forms a protective oxide layer — nickel is not always present in all grades.

Recent Developments (2024–2026)

Critical Minerals Mission — India's Strategic Metals Policy (2024–25)

India launched the National Critical Minerals Mission in 2024 with an outlay of ₹16,300 crore, identifying 30 critical minerals essential for clean energy, defence, and digital technologies — including lithium, cobalt, nickel, graphite, rare earth elements (REEs), and titanium. KABIL (Khanij Bidesh India Limited) secured lithium mining blocks in Argentina, cobalt in Australia, and rare earth exploration in strategic locations. CSIR-Central Road Research Institute also developed the world's first port road using recycled steel slag — an applied metals chemistry innovation.

UPSC angle: India's Critical Minerals Mission (2024, ₹16,300 crore) is the most significant metals policy development in recent years — directly relevant for GS3 questions on critical minerals, rare earth elements, and strategic resources.

Lithium Reserves — India's Jammu & Kashmir Discovery

India's Geological Survey of India (GSI) confirmed inferred lithium reserves of 5.9 million tonnes in Reasi district, Jammu & Kashmir in February 2023 — a discovery whose strategic implications continued to be assessed and developed in 2024–25. Lithium is the key metal in Li-ion batteries powering electric vehicles and energy storage. India's goal of 30% EV penetration by 2030 makes domestic lithium supply critically important.

UPSC angle: J&K lithium reserves are a high-frequency Prelims fact (5.9 million tonnes, Reasi) and a Mains anchor for critical minerals, EV policy, and energy security questions.

Vocabulary

Malleable

• Pronunciation: /ˈmælɪəbəl/
• Definition: Capable of being hammered, pressed, or rolled into thin sheets without breaking — a characteristic physical property of most metals, with gold being the most malleable.
• Origin: From Middle French malléable, from Late Latin malleābilis, from Latin malleāre (to hammer), from malleus (hammer); related to English mallet and maul.

Ductile

• Pronunciation: /ˈdʌktaɪl/
• Definition: Capable of being drawn out into thin wire by mechanical force without breaking — a property exhibited by metals such as gold, silver, and copper.
• Origin: From Latin ductilis (that may be led or drawn), from ductus, past participle of dūcere (to lead or draw); first recorded in English in the 14th century.

Alloy

• Pronunciation: /ˈælɔɪ/
• Definition: A homogeneous metallic substance composed of two or more elements, at least one of which is a metal, combined to achieve improved properties such as hardness, strength, or corrosion resistance.
• Origin: From Old French aloi, from aloier (to combine), from Latin alligāre (to bind together); the sense of "mixture of metals" arose in the mid-17th century.

Key Terms

Reactivity Series

• Pronunciation: /riːˌæktɪˈvɪti ˈsɪəriːz/
• Definition: An empirical ranking of metals in descending order of their tendency to lose electrons (undergo oxidation) and react with other substances such as water, acids, and metal salt solutions. The series runs from the most reactive metals (potassium, sodium, calcium) through moderately reactive metals (magnesium, aluminium, zinc, iron) to the least reactive noble metals (copper, silver, gold, platinum). It is used to predict displacement reactions (a more reactive metal displaces a less reactive metal from its salt solution) and to determine the most economical extraction method for each metal.
• Context: Built upon 19th-century electrochemistry experiments by Humphry Davy (isolated potassium and sodium by electrolysis, 1807) and Michael Faraday (laws of electrolysis, 1834). The key UPSC-relevant linkage is between reactivity and extraction method: highly reactive metals (K, Na, Ca, Al) are extracted by electrolysis of their molten ores (too reactive for carbon reduction); moderately reactive metals (Zn, Fe, Pb, Cu) are extracted by reduction with carbon/coke in blast furnaces; least reactive metals (Au, Pt, Ag) are found free in nature or extracted by simple methods. A more reactive metal can displace a less reactive one from solution -- e.g., iron displaces copper from copper sulphate solution (Fe + CuSO4 -> FeSO4 + Cu), which is the basis of copper purification.
• UPSC Relevance: GS3 (General Science / Economy). Prelims tests the order of reactivity (K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > [H] > Cu > Hg > Ag > Au > Pt), which metals react with dilute acids (only those above hydrogen in the series), extraction methods linked to reactivity (electrolysis/carbon reduction/found free), and displacement reactions. Know common alloy compositions -- stainless steel (Fe + Cr + Ni, corrosion-resistant), bronze (Cu + Sn), brass (Cu + Zn), duralumin (Al + Cu + Mg + Mn, used in aircraft), solder (Pb + Sn), and that German silver contains NO silver (Cu + Zn + Ni) -- a perennial Prelims trap. Mains connects to India's Critical Minerals Mission (2025), rare earth elements strategy, and mineral resource management.

Corrosion

• Pronunciation: /kəˈrəʊʒən/
• Definition: The gradual destruction of a metal or alloy by chemical or electrochemical reaction with its environment, most commonly involving oxidation in the presence of moisture, oxygen, and electrolytes (such as dissolved salts). Rusting of iron (Fe2O3.xH2O, hydrated iron oxide) is the most common form, requiring both oxygen and water -- it does not occur in dry air alone or in water free of dissolved oxygen. Corrosion costs the global economy an estimated 3-4% of GDP annually in infrastructure damage and maintenance.
• Context: Prevention methods tested in UPSC: galvanisation (coating iron with zinc, which corrodes preferentially as a sacrificial anode), electroplating (depositing a thin layer of a less reactive metal), painting/oiling (barrier method preventing contact with moisture), alloying (stainless steel contains 12-18% chromium, which forms a passive oxide layer), cathodic protection (using sacrificial anodes of zinc or magnesium on ships and pipelines), and anodising (thickening the natural oxide layer on aluminium). Green patina on copper (CuCO3.Cu(OH)2, basic copper carbonate) and black tarnish on silver (Ag2S, silver sulphide) are other common corrosion examples. India's Ashoka Pillar in Delhi (Iron Pillar of Mehrauli, ~1,600 years old) is remarkable for its corrosion resistance, attributed to its high phosphorus content forming a protective misawite layer.
• UPSC Relevance: GS3 (General Science / Economy). Prelims tests conditions for rusting (both oxygen AND water required), prevention methods (galvanisation, painting, alloying, sacrificial anode/cathodic protection, anodising), green patina on copper (basic copper carbonate), and black tarnish on silver (silver sulphide). Know alloy compositions: stainless steel (Fe + Cr + Ni, corrosion-resistant due to chromium oxide layer), bronze (Cu + Sn), brass (Cu + Zn), duralumin (Al + Cu + Mg + Mn, used in aircraft). The Delhi Iron Pillar's corrosion resistance (high phosphorus content) is a favourite factoid. Mains connects to infrastructure maintenance costs, marine corrosion of naval assets, and India's critical minerals and metallurgy sector.

Sources: NCERT Class 10 Science (Chapter 3 — Metals and Non-Metals), USGS Rare Earths Statistics, PIB press releases (Critical Minerals List, June 2023; KABIL; National Critical Mineral Mission, January 2025), Mining Technology (China REE production data, 2025), Indian Bureau of Mines (Bauxite, Mica Yearbooks), US Naval Academy (Corrosion Types course notes), Wikipedia (Reactivity Series, Duralumin, Rare-earth element, Metalloid, Stainless Steel, Nickel Silver).