Iron bridges, copper wires, oxygen in the air and sulfur in volcanoes belong to two families with very different behaviour. Learn how to tell them apart and predict their reactions.
Of the roughly 118 known elements, most are metals. Metals build our bridges, wires and vehicles; non-metals make up most of the air we breathe, our water and our bodies. Understanding why these two families behave so differently, and how to compare the reactivity of different metals, is a core part of chemistry.
On the periodic table, metals occupy the left and the centre, and non-metals are in the upper right (plus hydrogen, which sits at the top left but behaves as a non-metal). A staircase line separates them. Elements next to this line, such as silicon and germanium, have properties between the two and are called metalloids or semi-metals; they are important in electronics because they are semiconductors.
Most of the elements in the periodic table are metals. The most abundant metal in the Earth’s crust is aluminium, followed by iron. Iron is the most widely used metal in the world, mainly as steel.
| Property | Metals (typical) | Non-metals (typical) |
|---|---|---|
| Appearance | Shiny (lustrous) when clean | Dull |
| State at room temperature | Solid (except mercury) | Solids, liquids (bromine) or gases |
| Strength and shape | Strong; malleable (hammered) and ductile (drawn into wires) | Brittle if solid; shatter when hit |
| Electrical conductivity | Good conductors | Poor conductors (insulators), except graphite |
| Thermal conductivity | Good | Poor |
| Melting and boiling points | Usually high | Usually low |
| Density | Usually high | Usually low |
| Sound when struck | Sonorous (ring) | Dull thud |
These are general patterns, and there are exceptions. Mercury is a liquid metal. Sodium and potassium are soft enough to cut with a knife and have low melting points. Graphite, a form of carbon, conducts electricity, while diamond, also pure carbon, is extremely hard and does not conduct. Iodine is a shiny non-metal solid.
In a metal, the atoms lose their outer electrons and become positive ions arranged in a regular lattice. The outer electrons are delocalised: they are not attached to any one atom but move freely through the whole structure. The strong attraction between the positive ions and the sea of electrons is called metallic bonding.
An alloy is a mixture of a metal with one or more other elements. In an alloy, atoms of different sizes disturb the regular layers, so the layers slide less easily and the alloy is usually harder and stronger than the pure metal. Examples: steel (iron with a little carbon), brass (copper and zinc), bronze (copper and tin) and solder (tin and lead, or lead-free versions). Pure iron is too soft for most uses, so we nearly always use steel.
Metals tend to lose electrons to form positive ions (cations), such as Na⁺, Mg²⁺ and Al³⁺. Non-metals tend to gain electrons to form negative ions (anions), such as Cl⁻ and O²⁻, or to share electrons in covalent bonds.
| Oxides | Metal oxides | Non-metal oxides |
|---|---|---|
| Usual nature | Basic | Acidic (or neutral) |
| With water | Soluble ones give alkalis: Na₂O + H₂O → 2NaOH | Soluble ones give acids: SO₂ + H₂O → H₂SO₃ |
| With acids | React to form a salt and water | Do not react with acids |
| Examples | MgO, CuO, CaO | CO₂, SO₂, NO₂, P₄O₁₀; water and CO are neutral |
Some oxides, such as aluminium oxide and zinc oxide, are amphoteric: they react with both acids and strong alkalis. Acidic oxides are the cause of acid rain, which is why sulfur dioxide from burning fuels is a pollution problem.
The reactivity series arranges metals in order of how readily they react, that is, how easily they lose electrons. Carbon and hydrogen are added for comparison because they help predict extraction and reactions with acids.
| Metal | With cold water | With dilute acid | With air / oxygen |
|---|---|---|---|
| Potassium, sodium | Violent reaction; hydrogen and an alkali form | Explosive: not safe to try | Tarnish quickly; burn readily |
| Calcium | Steady fizzing; calcium hydroxide and hydrogen | Vigorous reaction | Burns |
| Magnesium | Very slow with cold water; reacts with steam to give MgO + H₂ | Fast reaction | Burns with a bright white flame |
| Zinc, iron | No reaction with cold water; react with steam | Moderate (zinc), slow (iron) | Slowly form oxide; iron rusts |
| Copper, silver, gold | No reaction | No reaction | Copper forms black CuO on heating; silver and gold are unreactive |
Examples: 2Na + 2H₂O → 2NaOH + H₂ and Ca + 2H₂O → Ca(OH)₂ + H₂. Aluminium is high in the series, but it appears unreactive because a thin, tough layer of aluminium oxide forms on its surface and protects the metal underneath. This is why aluminium is used for drinks cans, window frames and aircraft.
The reactivity series also predicts the thermal decomposition of metal carbonates: carbonates of very reactive metals such as sodium and potassium do not decompose in a Bunsen flame, but those of less reactive metals do. For example, green copper(II) carbonate decomposes when heated: CuCO₃ → CuO + CO₂ (it turns black).
Sodium, potassium and calcium react violently with water and must be handled only by teachers, with eye protection and safety screens. Alkali metals are stored under oil. Never touch them with your hands. Look away from the bright flame of burning magnesium.
A more reactive metal can displace a less reactive metal from a solution of its salt. The more reactive metal loses electrons (is oxidised) and the less reactive metal ions gain them (are reduced).
In the ionic form: Zn + Cu²⁺ → Zn²⁺ + Cu. When an iron nail is placed in blue copper(II) sulfate solution, a pink-brown coating of copper forms on the nail and the blue colour fades to pale green as iron(II) sulfate forms.
Question: Predict whether each reaction occurs, and write a word equation where it does: (a) magnesium + zinc sulfate; (b) copper + zinc sulfate.
Rule: a metal displaces any metal lower than itself in the series.
An ore is a rock that contains enough of a metal compound to make it worth extracting. The method depends on the metal’s position in the reactivity series: the more reactive the metal, the more energy is needed to extract it.
Iron is extracted from the ore haematite (mainly iron(III) oxide, Fe₂O₃) in a blast furnace. The raw materials are iron ore, coke (nearly pure carbon), limestone and hot air.
Question: What mass of iron can be made from 80 kg of iron(III) oxide, assuming complete reaction? (Ar: Fe = 56, O = 16)
Answer: 56 kg of iron. (Real furnaces give slightly less because of impurities and heat losses.)
| Non-metal | Key facts | Uses |
|---|---|---|
| Hydrogen | Lightest element; burns to form water | Making ammonia, fuel cells |
| Carbon | Diamond (hard, insulator) and graphite (soft, conducts) are different forms of the same element | Jewellery, cutting tools, pencils, electrodes, steelmaking |
| Nitrogen | About 78% of air; unreactive gas | Fertilisers (via ammonia), preserving food |
| Oxygen | About 21% of air; supports burning and respiration | Hospitals, steelmaking, welding |
| Sulfur | Yellow solid | Making sulfuric acid, rubber hardening |
| Chlorine | Toxic green-yellow gas | Disinfecting water, bleach, making PVC |
| Noble gases (helium, neon, argon) | Very unreactive because their outer shells are full | Balloons and airships (helium), signs (neon), light bulbs and welding (argon) |
The halogens (Group 17) are fluorine, chlorine, bromine and iodine. At room temperature chlorine is a green-yellow gas, bromine a red-brown liquid and iodine a grey-black solid that gives a purple vapour. Unlike metals, reactivity decreases down the group. A more reactive halogen displaces a less reactive one from its salt solution:
Chlorine displaces bromine (the solution turns orange-brown); bromine displaces iodine, but iodine cannot displace bromine or chlorine.
Chlorine, bromine and iodine vapours are harmful to breathe and irritate the eyes and lungs. Halogen reactions are teacher demonstrations in a fume cupboard.
Metals are a finite resource, and mining and extracting them affect the environment through habitat loss, energy use and waste. Recycling metals such as aluminium, iron and copper saves ores and energy, and reduces waste. Preventing corrosion, for example by painting, galvanising and sacrificial protection, makes metal objects last longer. Choosing the right material for each job, based on properties such as strength, density, conductivity and cost, is a key part of engineering.
Try each question first, then tap it to reveal the answer.
Answer: Delocalised electrons are free to move through the metal and carry charge.
Answer: Steel is harder and stronger because the added carbon atoms disrupt the layers of iron atoms.
Answer: Yes, because zinc is more reactive than copper and so takes its place.
Answer: Sodium + water → sodium hydroxide + hydrogen.
Answer: It decomposes to calcium oxide, which reacts with silica (sand) impurities to form slag.
Answer: Carbon dioxide; green to black.
Answer: Chlorine, because halogen reactivity decreases down Group 17.
Suggested use: have students test samples of several metals and non-metals for conductivity with a simple circuit and sort them, then compare magnesium, zinc and copper with dilute acid and record the speed of bubbling. Reactions of alkali metals and halogens are teacher demonstrations only. Parents can use household objects (foil, cables, pans, coins, pencil lead) to discuss properties and uses. Please follow your own syllabus for the required details of extraction and trends.
These reputable sources were consulted to verify the facts in this article:
Copyright note: This article is original EDUSAMBAM educational writing. The diagrams are original inline SVG schematics created for this page and are not copied from any source. Links open external websites; the sources were used to check facts and are suggested for further study.
Last updated: 21 October 2026. Written for students up to age 18 and checked against standard school-level chemistry references. This is general education, not a substitute for your teacher, textbook or syllabus.
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