Transition Elements
Section: 8. The Periodic Table | Syllabus: Cambridge IGCSE Chemistry (0620)
Properties of Transition Elements
Transition elements occupy the central block of the Periodic Table (e.g. Sc to Zn, including iron, copper, and platinum). As metals they are:
- high density
- high melting point
- form coloured compounds
- often act as catalysts, both as the element and in compounds
| Compound | Colour |
|---|---|
| Copper(II) sulfate | blue |
| Iron(III) oxide | red-brown |
| Potassium manganate(VII) | purple |
Catalytic uses seen elsewhere in the course: iron in the Haber process, vanadium(V) oxide in the Contact process, manganese(IV) oxide decomposing hydrogen peroxide, platinum in catalytic converters.
Worked Example: Identifying a General Property
- Question: platinum is a transition metal. Which statement about it is correct? (A) it does not catalyse reactions (B) it forms coloured compounds (C) it has a low density (D) it has a low melting point [1]
- Answer: B. Platinum forms coloured compounds, like other transition metals. It IS a well-known catalyst (ruling out A), and it has a very high density and melting point, not low (ruling out C and D).
Worked Example: Stating Two Properties
- Question: titanium is a transition element used as a catalyst. State two other properties of transition elements. [2]
- Answer: any two of - high density; high melting/boiling point; form coloured compounds
Variable Oxidation Numbers
Unlike Group I/II metals, transition elements commonly form ions with more than one possible charge (variable oxidation number).
| Ion | Name | Typical compound colour |
|---|---|---|
| Fe²⁺ | iron(II) | pale green (e.g. FeSO₄) |
| Fe³⁺ | iron(III) | orange/brown (e.g. FeCl₃) |
The Roman numeral in a transition metal's name shows which oxidation number is present, e.g. iron(II) chloride (FeCl₂) vs. iron(III) chloride (FeCl₃).
Common Mistakes
- ❌ Thinking transition metals form positive ions by GAINING electrons
- ✓ like all metals, they form positive ions by LOSING electrons - what's distinctive is that they can lose a variable number, giving more than one possible ion
- ❌ Saying transition metals "only form white compounds"
- ✓ the opposite is true - forming coloured compounds is one of their defining characteristics
Interactive revision notes, videos and practice questions load below.