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Learn0620Papers 1, 3 · CoreThe Periodic TableTransition elements and noble gases
The Periodic Table · Subtopic 3 of 3

Transition Elements and Noble Gases

Transition elements (the central block, e.g. Fe, Cu, Ni, Cr) are hard, dense metals with high melting points. They form coloured compounds, have ions with variable oxidation numbers (iron(II) and iron(III)) and are often catalysts (iron in the Haber process). Noble gases (group VIII/0) have full outer shells, so they are unreactive and exist as single atoms; helium is used in balloons, argon in light bulbs and welding.

Cambridge 5070 Paper 1Cambridge 5070 Paper 2Cambridge 0620 Papers 2, 4Cambridge 0620 Papers 1, 3Edexcel 4CH1 Paper 1CEdexcel 4CH1 Paper 2C≈ 25 minRevision 1 · updated 2026-10-30
Section 1 of 14

Learning objectives

  • Describe the properties of transition elements.
  • Compare transition metals with group I metals.
  • Explain the unreactivity of noble gases and give their uses.
Pause and think

Copper(II) sulfate is blue, iron(III) chloride is orange-brown, but sodium chloride is white. What makes the difference?

Section 2 of 14

Core idea

Start hereColourful metals

Rubies are red because of chromium; sapphires blue because of iron and titanium; old copper roofs turn green. The colours come from transition metal ions.

The big idea

Transition metals are hard, dense and high-melting, form coloured ions with variable charges, and make excellent catalysts. Noble gases, with full outer shells, barely react at all.

1. Transition metals

Worked exampleNaming with Roman numerals

Name FeCl2\mathrm{FeCl_2} and FeCl3\mathrm{FeCl_3}.

Goal
Names showing the charge.
Strategy
Each Cl is −1-1.
  1. FeCl2: Fe2+\mathrm{FeCl_2}:\ \mathrm{Fe^{2+}}
    Two chloride ions balance +2+2.
  2. FeCl3: Fe3+\mathrm{FeCl_3}:\ \mathrm{Fe^{3+}}
    Three chloride ions balance +3+3.
AnswerIron(II) chloride and iron(III) chloride.
✓ CheckPale green and yellow-brown solutions ✓.
Transition metal properties

Four properties to remember.

2. Noble gases

  • Helium: balloons, airships (low density, non-flammable).
  • Neon: advertising lights.
  • Argon: light bulbs, welding shield (inert).
Edge caseNot completely inert Xenon can be forced to react with fluorine to make XeF4\mathrm{XeF_4}. "Unreactive" is a strong tendency, not an absolute rule.
Pause and think

Why does a catalyst make industrial processes cheaper?

Summary

  • Transition: dense, coloured, variable charge, catalysts.
  • Noble gases: full shells, monatomic.
Key words
Transition element
A metal in the central block of the Periodic Table.
Oxidation number
Charge an atom would have; shown by Roman numerals.
Monatomic
Existing as single atoms.
HistoryRamsay. William Ramsay discovered argon, neon, krypton and xenon in the 1890s, adding a whole new group to the Periodic Table, and won the 1904 Nobel Prize.
Fun factHelium voices. Breathing helium makes your voice squeaky because sound travels about three times faster in helium than in air.
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