Skip to main content

Transition elements; oxidation states of 3d; alloys

Short answer

Transition elements have partly filled d-subshell. Variable oxidation states occur because 4s and 3d electrons have similar energy, enabling both to bond; states differ by one unit (e.g., Mn +2 to +7). Alloy formation is possible due to similar atomic radii, allowing atom substitution in lattices, e.g., steel and brass.

What are transition elements? Explain the variable oxidation states exhibited by 3d series. Why does the transition elements form alloy?

Transition elements

Transition elements are the d-block elements that have a partly filled d-subshell in the atom or in at least one of their common oxidation states. The 3d series is Sc to Zn (general outer configuration (n−1)d¹⁻¹⁰ ns¹⁻²).

Variable oxidation states

Variable oxidation states arise because the 4s and 3d electrons have very similar energies, so both 4s and some or all 3d electrons can be used in bonding. The states differ by one unit (Fe²⁺, Fe³⁺), unlike the p-block where they differ by two.

Ti  +2 +3 +4          Fe  +2 +3
V   +2 +3 +4 +5       Co  +2 +3
Cr  +2 +3 +6          Ni  +2
Mn  +2 +3 +4 +6 +7    Cu  +1 +2
  • Minimum oxidation state is usually +2 (loss of the two 4s electrons); the maximum equals the total number of 4s + 3d electrons, reached at Mn (+7).
  • Stability of higher states falls after Mn because the nuclear charge holds the 3d electrons more tightly.
  • Half-filled d⁵ (Mn²⁺, Fe³⁺) and filled d¹⁰ (Zn²⁺) are specially stable.

Alloy formation

Transition metals have similar atomic radii, so atoms of one metal can replace atoms of another in the crystal lattice without disturbing the structure. They therefore form alloys readily, such as steel (Fe–C–Cr–Ni), brass (Cu–Zn) and bronze (Cu–Sn).

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Engineering Chemistry chapter 5 questions →