Metals and Non-metals
How elements are sorted into metals and non-metals by their physical and chemical properties, and how metals are ranked from most to least reactive in the activity series.
Basic chemistry of metals and non-metals is a steady Prelims staple under Science & Technology — expect direct facts on the reactivity series, amphoteric oxides, aqua regia, allotropes of carbon and 'odd property' identification. For Mains it feeds GS-III (science in everyday life, materials and corrosion), where knowing why a specific metal is chosen for a specific use adds value. The reactivity-and-oxide logic also underpins later topics like metallurgy and electrochemistry.
Understand the chapter
Physical Properties of Metals
In their pure state metals share a recognisable cluster of physical traits, but these alone cannot classify elements because exceptions exist. Metals are lustrous, generally hard, malleable, ductile, sonorous, and good conductors of heat and electricity with high melting points.
- Malleability: can be beaten into thin sheets — gold and silver are the most malleable.
- Ductility: can be drawn into wires — gold is the most ductile; 1 g of gold gives a wire about 2 km long.
- Heat conduction: silver and copper are the best conductors; lead and mercury are poor.
- Sonorous: produce a ringing sound on striking — why school bells and gongs are metallic.
Non-metals and the Blurred Boundary
Non-metals are far fewer than metals and exist as solids or gases, with bromine the only liquid. Physical properties alone fail to classify elements cleanly because several cases cross the metal/non-metal line, so chemical behaviour gives the sharper test.
- Mercury is the only metal liquid at room temperature; gallium and caesium melt in the palm (very low melting points).
- Iodine is a non-metal yet lustrous — an exception to the 'dull non-metal' rule.
- Carbon allotropes: diamond is the hardest natural substance; graphite conducts electricity.
- Alkali metals (Li, Na, K) are soft enough to cut with a knife, with low density and low melting points.
Reaction with Oxygen: Metal Oxides
Almost all metals combine with oxygen to form metal oxides, which are generally basic, while non-metals form acidic oxides. Reactivity toward oxygen varies sharply — sodium and potassium ignite in open air, whereas silver and gold resist oxygen even when hot.
- Soluble basic oxides give alkalis: Na2O gives NaOH, K2O gives KOH.
- Amphoteric oxides (Al2O3, ZnO) react with both acids and bases to give salt and water.
- A thin protective oxide layer on Mg, Al, Zn, Pb prevents further oxidation; anodising deliberately thickens aluminium's layer.
- Na and K are so reactive they catch fire in air, so they are stored under kerosene oil.
Reaction with Water and Acids
Metals react with water to give a metal oxide or hydroxide and hydrogen gas, but reactivity falls steeply down the activity order. With dilute acids metals give salt plus hydrogen — except nitric acid, which being a strong oxidiser usually yields no hydrogen.
- Water: K, Na violent in cold water (H2 ignites); Ca gentler and floats; Mg only in hot water; Al, Fe, Zn only with steam; Pb, Cu, Ag, Au not at all.
- Dilute HCl reactivity order: Mg > Al > Zn > Fe; copper does not react.
- HNO3 oxidises the H2 to water and is itself reduced to nitrogen oxides (N2O, NO, NO2).
- Exception: very dilute HNO3 with magnesium (Mg) and manganese (Mn) does evolve H2 gas.
Displacement and the Reactivity Series
A more reactive metal displaces a less reactive one from its salt solution, giving the clearest evidence of relative reactivity. Compiling these displacement results yields the activity series, running from potassium (most reactive) down to gold (least reactive).
- Activity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au.
- Metals above hydrogen displace H2 from dilute acids; those below it do not.
- Iron nail in copper sulphate deposits copper and turns the blue solution pale — proof iron is more reactive than copper.
Named Reagents and Processes
A few named reagents and industrial processes recur in exams because they exploit reactivity and oxide chemistry. Aqua regia uniquely dissolves the noble metals, and anodising is a practical application of aluminium's oxide layer.
- Aqua regia ('royal water'): 3:1 mixture of concentrated HCl to concentrated HNO3; dissolves gold and platinum, which neither acid alone can.
- Anodising: aluminium is made the anode and electrolysed with dilute sulphuric acid to build a thick, dye-able, corrosion-resistant oxide layer.
Key terms
- Metallic lustre
- The characteristic shining surface of a metal in its pure state.
- Malleability
- Ability of a metal to be beaten into thin sheets; gold and silver are the most malleable.
- Ductility
- Ability of a metal to be drawn into thin wires; gold is the most ductile.
- Sonorous
- Producing a ringing sound when struck, as metals do.
- Allotrope
- One of the different physical forms of the same element, e.g., diamond and graphite of carbon.
- Amphoteric oxide
- An oxide that reacts with both acids and bases to give salt and water (Al2O3, ZnO).
- Alkali
- A water-soluble base formed when oxides like Na2O and K2O dissolve in water.
- Reactivity (activity) series
- A list of metals arranged in order of decreasing reactivity, from potassium to gold.
- Aqua regia
- A 3:1 mixture of concentrated HCl and HNO3 that can dissolve gold and platinum.
- Anodising
- An electrolytic process that thickens aluminium's protective oxide layer for corrosion resistance.
Must-know facts exam-ready
- Mercury is the only metal that is liquid at room temperature.
- Bromine is the only non-metal that is liquid; the rest are solids or gases.
- Gold is the most ductile metal — 1 g of gold can be drawn into a wire about 2 km long.
- Gold and silver are the most malleable metals.
- Silver and copper are the best conductors of heat; lead and mercury are poor conductors.
- Diamond (an allotrope of carbon) is the hardest natural substance; graphite conducts electricity.
- Gallium and caesium have such low melting points that they melt in the palm of the hand.
- Reactivity series: K, Na, Ca, Mg, Al, Zn, Fe, Pb, [H], Cu, Hg, Ag, Au.
- Amphoteric oxides in the chapter are aluminium oxide (Al2O3) and zinc oxide (ZnO).
- Aqua regia is 3 parts concentrated HCl to 1 part concentrated HNO3 and dissolves gold and platinum.
- Reactivity with dilute HCl: Mg > Al > Zn > Fe; copper does not react.
- Sodium and potassium are stored under kerosene oil to prevent them catching fire.
Memory tricks remember it for good
Traps to avoid
- 'All metals are solid' is false — mercury is liquid, and gallium and caesium melt near body temperature.
- 'All non-metals are dull and non-conducting' is false — iodine is a lustrous non-metal and graphite (carbon) conducts electricity.
- Most ductile/malleable (gold) is the LEAST reactive metal — do not confuse softness/workability with reactivity.
- 'All metals + acid gives hydrogen' is false — nitric acid usually gives no H2 (it oxidises it), and copper does not react with dilute HCl at all.
- Aqua regia ratio is 3:1 HCl:HNO3, not 1:3; and it dissolves gold/platinum that neither acid alone can.
- Amphoteric oxides are only specific metal oxides (Al2O3, ZnO); most metal oxides are basic and most non-metal oxides are acidic.
Exam focus
🧠 Prelims angles
- Property-matching and odd-one-out: most malleable (Au, Ag), most ductile (Au), best heat conductor (Ag, Cu), only liquid metal (Hg), only liquid non-metal (Br).
- Reactivity series ordering and displacement: which metal displaces which from a salt solution.
- Identifying amphoteric oxides (Al2O3, ZnO) and classifying oxides as acidic or basic.
- Aqua regia composition (3:1 HCl:HNO3) and the metals it dissolves (gold, platinum).
- Allotropes of carbon: diamond (hardest) versus graphite (conducts electricity).
- Handling and processes: storage of Na and K in kerosene, and anodising of aluminium.
✍️ Mains angles GS-III
- How do the physical properties of metals and non-metals translate directly into their everyday uses?Map malleability and ductility to wires and vessels, conductivity to electrical wiring, sonority to bells, and contrast with non-metal exceptions like graphite and iodine.
- Explain how metallic reactivity and oxide chemistry govern corrosion and the choice of materials.Use NCERT cases — protective oxide layers and anodising of aluminium, kerosene storage of alkali metals, and the inertness of noble metals (Au, Ag) for jewellery and contacts.
- Discuss how a metal's position in the reactivity series determines how easily it can be obtained and handled.Link high reactivity (K, Na, Ca) to violent reactions and careful storage, and low reactivity (Cu, Ag, Au) to free or easy availability; ground only in the activity series and displacement logic given.
Last-minute revision tick as you recall
- Only liquid metal = mercury; only liquid non-metal = bromine.
- Most malleable/ductile = gold (also least reactive); best heat conductors = silver and copper.
- Diamond = hardest natural substance; graphite = the non-metal that conducts electricity.
- Amphoteric oxides = Al2O3 and ZnO (react with both acids and bases).
- Activity series: K Na Ca Mg Al Zn Fe Pb [H] Cu Hg Ag Au.
- Water reactivity: K/Na (cold, fiery) > Ca (cold, floats) > Mg (hot) > Al/Fe/Zn (steam) > Cu/Pb/Ag/Au (none).
- Dilute HCl: Mg > Al > Zn > Fe; copper no reaction; HNO3 gives no H2 as it is an oxidiser.
- Aqua regia = 3:1 concentrated HCl:HNO3; dissolves gold and platinum.
- Na and K stored under kerosene; anodising thickens aluminium's protective oxide layer.
Distilled from NCERT Class 10 · Science (Class 10) for UPSC. Always cross-check facts with the original NCERT.