Transition Elements
Section: 8. The Periodic Table | Syllabus: Cambridge AS Level Physics 9702
Introduction to Transition Elements Transition elements (or transition metals) are located in the central block of the Periodic Table, between Groups 2 and 13. They have unique properties that make them very important in industry and everyday life.
Transition Elements Metallic elements found in Groups 3-12 of the Periodic Table that have partially filled d-orbitals and can form multiple ions with different charges. Common Transition Elements Element Symbol Atomic Number Common Uses Scandium Sc 21 Aerospace alloys Titanium Ti 22 Aircraft, medical implants Iron Fe 26 Steel, construction Copper Cu 29 Electrical wiring, coins Zinc Zn 30 Galvanizing, brass Silver Ag 47 Jewelry, electronics Gold Au 79 Jewelry, electronics Location in Periodic Table Transition elements form the "d-block" in the middle of the Periodic Table.
They fill the 3d, 4d, and 5d electron shells. Diagram Periodic Table with transition metals block (Groups 3-12) highlighted in color, showing their central position Physical Properties Transition metals share many common physical properties that distinguish them from Group 1 and 2 metals.
General Physical Properties High melting points - generally much higher than Group 1 and 2 metals High density - denser than most other metals Hard and strong - useful for construction and tools Good conductors of heat and electricity Lustrous (shiny) when polished Malleable and ductile - can be shaped and drawn into wires Metal Melting Point (°C) Density (g/cm³) Hardness Sodium (Group 1) 98 0.97 Soft Iron (Transition) 1538 7.87 Hard Copper (Transition) 1085 8.96 Hard Tungsten (Transition) 3422 19.25 Very hard Why Are They Strong?
Transition metals have strong metallic bonding due to having more electrons available for bonding. This creates stronger attractions between metal ions and delocalized electrons, resulting in high melting points and strength.
Diagram Bar chart comparing melting points and densities of Group 1 metal (sodium) versus transition metals (iron, copper, tungsten) Chemical Properties Transition metals have distinctive chemical properties that make them different from other metals.
Variable Oxidation States Transition metals can form ions with different charges (multiple oxidation states). Metal Common Oxidation States Examples Iron +2, +3 Fe²⁺ (iron(II)), Fe³⁺ (iron(III)) Copper +1, +2 Cu⁺ (copper(I)), Cu²⁺ (copper(II)) Chromium +2, +3, +6 Cr²⁺, Cr³⁺, Cr₂O₇²⁻ Manganese +2, +4, +7 Mn²⁺, MnO₂, MnO₄⁻ Can lose different numbers of electrons Form compounds with different formulas (e.g., FeO and Fe₂O₃) Group 1 and 2 metals only form one type of ion Colored Compounds Many transition metal compounds are colored , unlike most Group 1 and 2 compounds which are white.
Compound Color Use Copper(II) sulfate (CuSO₄) Blue Algicide, fungicide Iron(III) oxide (Fe₂O₃) Red-brown (rust) Pigment, iron ore Chromium(III) oxide (Cr₂O₃) Green Pigment (chrome green) Potassium manganate(VII) (KMnO₄) Purple Disinfectant, oxidizing agent Colors arise from electron transitions in d-orbitals Different oxidation states have different colors Useful for identifying compounds Used as pigments in paints and dyes Why Are They Colored?
When light hits transition metal compounds, electrons in the d-orbitals absorb certain wavelengths and jump to higher energy levels. The remaining wavelengths are reflected, giving the compound its color.
Diagram Test tubes showing colored solutions: blue CuSO₄, green Cr₂O₃, purple KMnO₄, and brown Fe₂O₃ Catalytic Properties Transition metals and their compounds are excellent catalysts . Catalyst A substance that speeds up a chemical reaction without being used up itself.
Industrial Catalysts Catalyst Process Reaction Iron Haber Process N₂ + 3H₂ ⇌ 2NH₃ (ammonia production) Vanadium(V) oxide Contact Process 2SO₂ + O₂ → 2SO₃ (sulfuric acid production) Nickel Hydrogenation Vegetable oils → margarine Platinum Catalytic converters Converts toxic exhaust gases to less harmful substances Manganese(IV) oxide Decomposition 2H₂O₂ → 2H₂O + O₂ Provide alternative reaction pathways with lower activation energy Can use different oxidation states during catalysis Surface area important - often used as fine powders or on supports Essential for many industrial processes Why Good Catalysts?
Transition metals can change oxidation states easily, allowing them to form temporary bonds with reactants. This lowers the activation energy and speeds up the reaction. Reactivity Transition metals are generally less reactive than Group 1 and 2 metals.
Comparison with Alkali Metals Property Group 1 Metals Transition Metals Reactivity Very reactive Less reactive Reaction with water Vigorous (produce H₂) Slow or no reaction (except with steam) Reaction with oxygen Fast, tarnish quickly Slower, resistant to corrosion Storage Must store under oil Can be stored in air Corrosion Resistance Many transition metals resist corrosion Gold and platinum are very unreactive (noble metals) Chromium and nickel form protective oxide layers I…
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