The d- and f-Block Elements

Notes

The d- and f-Block Elements

The d- and f-block elements form an important part of inorganic chemistry. The d-block elements are generally known as transition elements, while the f-block elements are known as inner transition elements.

1. d-Block Elements

The elements in which the last electron enters the (n−1)d orbital are called d-block elements.

General electronic configuration:

(n−1)d^1–10 ns^0–2

The d-block elements are placed between the s-block and p-block elements in the periodic table.

2. Transition Elements

Transition elements are those elements which have partially filled d-orbitals in their atoms or in at least one of their common oxidation states.

Most d-block elements are transition elements. However, Group 12 elements such as Zn, Cd and Hg are generally not considered transition elements because their atoms and common ions have completely filled d-orbitals.

Example:

Zn = [Ar] 3d¹⁰4s²

Zn²⁺ = [Ar] 3d¹⁰

3. Electronic Configuration of d-Block Elements

The general electronic configuration of d-block elements is:

(n−1)d^1–10 ns^0–2

First Transition Series (3d Series)

The first transition series extends from scandium (Sc) to zinc (Zn).

• Sc: [Ar] 3d¹4s²
• Ti: [Ar] 3d²4s²
• V: [Ar] 3d³4s²
• Cr: [Ar] 3d⁵4s¹
• Mn: [Ar] 3d⁵4s²
• Fe: [Ar] 3d⁶4s²
• Co: [Ar] 3d⁷4s²
• Ni: [Ar] 3d⁸4s²
• Cu: [Ar] 3d¹⁰4s¹
• Zn: [Ar] 3d¹⁰4s²

Chromium and copper show exceptional electronic configurations because half-filled and completely filled d-subshells have extra stability.

4. General Characteristics of Transition Elements

• Metallic character
• High melting points
• High enthalpy of atomisation
• Variable oxidation states
• Formation of coloured ions and compounds
• Catalytic properties
• Formation of interstitial compounds
• Alloy formation
• Magnetic properties
• Complex formation

5. Metallic Character

Transition elements are metals. They are generally hard, malleable and ductile and possess good thermal and electrical conductivity.

The metallic character is associated with strong metallic bonding involving the valence electrons.

Greater participation of unpaired electrons generally results in stronger metallic bonding.

6. Melting Points

Transition metals generally have high melting points because of strong metallic bonding.

The strength of metallic bonding depends upon the number of electrons available for bonding.

In the first transition series, melting points generally rise towards the middle of the series and then decrease.