Metals are elements that lose electrons easily to form positive ions. They are characterised by lustre, conductivity, malleability and ductility. CBSE Class 10 introduces metals; Class 11 and 12 expand. NEET tests properties and specific metals.
Core Concepts
Physical properties
Lustre, high conductivity (thermal and electrical), malleability, ductility, sonorous, high density, high melting point (with exceptions like mercury and sodium). Most are solids at room temperature.
Some notable exceptions that NEET loves to test:
- Mercury — only metal that is liquid at room temperature
- Gallium and caesium — melt near body temperature (Ga: 29.8°C, Cs: 28.4°C)
- Sodium and potassium — soft enough to cut with a knife, low density (Na and K float on water)
- Tungsten — highest melting point among metals (3422°C), used in light bulb filaments
- Silver — best conductor of electricity and heat (copper is second)
- Gold — most malleable metal (can be beaten into sheets a few atoms thick)
- Platinum — most ductile (can be drawn into the thinnest wire)
Chemical properties
React with oxygen to form oxides (usually basic). React with water — very active with cold water (Na), less active with hot water (Mg), unreactive (Au). React with acids to release hydrogen (except Cu, Ag, Au).
Let us look at these reactions systematically:
Metals + Oxygen:
Most metal oxides are basic (react with acids). Some are amphoteric — Al2O3 and ZnO react with both acids and bases. This is a common NEET question.
Metals + Water:
| Metal | Reaction with Water | Products |
|---|---|---|
| Na, K | Cold water (vigorous) | Metal hydroxide + H2 |
| Ca | Cold water (less vigorous) | Ca(OH)2 + H2 |
| Mg | Hot water (slow) | Mg(OH)2 + H2 |
| Al, Zn, Fe | Steam only | Metal oxide + H2 |
| Cu, Ag, Au | No reaction | - |
Metals + Dilute acids:
Metals above hydrogen in the reactivity series displace H2 from dilute acids. Cu, Ag, and Au are below hydrogen and do not react with dilute HCl or H2SO4.
Copper does react with concentrated H2SO4 (hot) and HNO3 (any concentration), but not with dilute HCl or dilute H2SO4. This distinction is frequently tested.
Reactivity series
K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, H, Cu, Hg, Ag, Au. More reactive metals displace less reactive ones from their salt solutions. The position determines extraction method and corrosion resistance.
| Metal | Reactivity | Extraction Method |
|---|---|---|
| K, Na, Ca, Mg, Al | Very reactive | Electrolysis of molten salt |
| Zn, Fe, Sn, Pb | Moderately reactive | Carbon reduction (smelting) |
| Cu, Hg, Ag, Au | Least reactive | Roasting/self-reduction or found native |
A quick way to remember the series: King Nates Can Make All Zombies In Short Periods Happy Calling Happy Singing Goldfishes (K, Na, Ca, Mg, Al, Zn, Fe (Iron), Sn, Pb, H, Cu, Hg, Ag, Au).
Ionic compounds of metals
Metals lose electrons to form cations. React with non-metals to form ionic compounds. NaCl, MgO, Al2O3 are typical examples.
Properties of ionic compounds:
- High melting and boiling points (strong electrostatic attraction between ions)
- Conduct electricity when molten or in solution (ions are free to move)
- Soluble in water (polar solvent dissolves ionic substances)
- Hard but brittle (layers of ions slide and repel when a force is applied)
Some specific metals
Iron (most used, extracted in blast furnace). Aluminium (second most used, extracted electrolytically). Copper (excellent conductor, used in wiring). Gold (unreactive, used in jewellery and electronics).
Worked Examples
Sodium reacts violently with oxygen and water. Kerosene is non-polar, keeps oxygen and water out, and does not react with sodium. Safe storage.
Delocalised electrons in the metallic bond can move freely through the lattice, carrying current (electrical) and thermal energy.
Will iron displace copper from CuSO4 solution? Check the reactivity series: Fe is above Cu. Yes, iron will displace copper.
The iron nail gets coated with brown copper. The blue solution turns green (FeSO4). This is a classic CBSE practical exam question.
Aluminium is quite reactive (above zinc in the series), but it forms a thin, tough layer of Al2O3 on its surface. This oxide layer is impervious to air and water, preventing further reaction. This is called passivation. Anodising makes this layer even thicker for cookware and building materials.
Aluminium is above iron in the reactivity series, so it can displace iron from its oxide. This reaction is extremely exothermic (temperatures above 2000°C) and is used to weld railway tracks.
Common Mistakes
Saying all metals react with water. Gold and platinum do not.
Confusing malleable (sheets) with ductile (wires).
Writing that mercury is solid at room temperature. It is liquid.
Saying aluminium is unreactive because it does not visibly corrode. It is actually quite reactive — it just has a protective oxide layer. Remove the oxide (e.g., with mercury amalgamation) and aluminium reacts vigorously with air and water.
Writing that a more reactive metal always displaces a less reactive one. This is true in aqueous solution, but not always in the solid state. The thermite reaction works because the oxide is reduced, not a salt solution.
Exam Weightage and Revision
Metals and Non-metals is a major chapter in CBSE Class 10 (8-10 marks). NEET tests metal properties, reactivity series predictions, and extraction methods. JEE focuses on electrochemistry and metallurgy in separate chapters. This chapter is foundational — understanding reactivity series unlocks predictions across multiple topics.
| Question Type | Exam | Frequency |
|---|---|---|
| Reactivity series prediction | CBSE, NEET | Every year |
| Metal-water reactions | CBSE | Most years |
| Displacement reactions | CBSE, NEET | Every year |
| Metal oxide nature (basic/amphoteric) | NEET | Every 2 years |
| Extraction method by reactivity | CBSE, NEET | Most years |
The single most important thing to memorise is the reactivity series. With it, you can predict which metal displaces which, which metals react with water, which react with acids, and how each is extracted. One list, dozens of answers.
Practice Questions
Q1. Arrange the following metals in order of decreasing reactivity: Fe, Na, Cu, Au, Mg.
Na > Mg > Fe > Cu > Au. From the reactivity series: sodium is most reactive (reacts with cold water), followed by magnesium (reacts with hot water), iron (reacts with steam), copper (below hydrogen, does not react with dilute acids), and gold (least reactive, found native).
Q2. Why can aluminium vessels be used for cooking even though aluminium is above iron in the reactivity series?
Aluminium forms a thin, stable layer of aluminium oxide (Al2O3) on its surface when exposed to air. This oxide layer is chemically inert and prevents further reaction of the aluminium with food or water. This passivation makes aluminium safe for cooking despite its position in the reactivity series.
Q3. What happens when zinc granules are added to CuSO4 solution? Give the balanced equation and explain.
Zinc displaces copper because Zn is above Cu in the reactivity series:
The blue colour of CuSO4 solution fades (Cu2+ ions are removed) and a reddish-brown deposit of copper appears on the zinc granules. The solution becomes colourless (ZnSO4 is colourless).
Q4. Why is gold found in nature in the native (free) state while sodium is always found in combined form?
Gold is at the bottom of the reactivity series — it is extremely unreactive. It does not react with oxygen, water, or common acids, so it remains in its elemental form in nature. Sodium is at the top of the reactivity series — it is highly reactive and immediately combines with oxygen and water. It is always found as NaCl, Na2CO3, or other salts.
FAQs
Why is copper used in electrical wiring instead of silver?
Silver is a better conductor, but copper is much cheaper and almost as good (97% of silver’s conductivity). For the vast amounts of wire needed in buildings and power grids, the cost difference makes copper the practical choice.
Can a less reactive metal displace a more reactive one?
Not under normal conditions. The reactivity series is based on standard electrode potentials. However, under extreme conditions (like the thermite reaction at very high temperatures), unusual displacements can occur because the reaction is thermodynamically favourable due to the very stable oxide product.
Why do we use coke (carbon) to extract iron but electrolysis for aluminium?
Carbon can reduce iron oxide because iron is moderately reactive. But aluminium has a higher affinity for oxygen than carbon does, so carbon cannot reduce Al2O3. We need electrolysis (a stronger reducing method) for very reactive metals.
Memorise reactivity series at least up to iron. Many NEET questions depend on predicting which metal displaces which.
Metals are the backbone of industry and technology. Learning their reactivity order unlocks most predictions in inorganic chemistry.