Introduction to d and f-Block Elements

This section explores d-block and f-block elements, also known as transition metals. These elements exhibit unique properties that bridge the gap between the highly reactive s-block metals and the covalent p-block elements.

Defining Transition Metals

Transition metals are characterized by the presence of partially filled d-orbitals in their atomic state or in common oxidation states. These d-orbitals are located between the s and p orbitals and play a crucial role in their chemical behavior. They are further categorized as d-block (if the partially filled orbitals are d) or f-block (if the partially filled orbitals are f) elements.

Why the Name “Transition Metals”?

The term “transition” reflects the position of these elements in the periodic table. Their properties lie between the highly electropositive s-block metals (Group IA and IIA) that readily form ionic bonds and the p-block elements (Groups IIIA-VIIIA) that often form covalent bonds. Transition metals exhibit a blend of both ionic and covalent character, showcasing a transition in behavior.

Exploring the Series of Transition Metals

The d-block elements consist of three series, each containing ten elements:

• 1st Series (3d-series): Sc (Scandium) to Zn (Zinc) (Elements 21 to 30) – Electronic Configuration: (n-1)d¹-¹ºns² (e.g., Sc: 3d¹4s²)
• 2nd Series (4d-series): Y (Yttrium) to Cd (Cadmium) (Elements 39 to 48) – Electronic Configuration: (n-1)d¹-¹ºns² (e.g., Y: 4d¹5s²)
• 3rd Series (5d-series): La (Lanthanum) to Hg (Mercury) (Elements 57 to 80) – Electronic Configuration: (n-1)d¹-¹ºns² (e.g., La: 5d¹6s²)

f-Block Elements:

The f-block elements also belong to the transition metal category and consist of two series:

• 4f-series (Lanthanides): Ce (Cerium) to Lu (Lutetium) (Elements 58 to 71)
• 5f-series (Actinides): Ac (Actinium) to Lr (Lawrencium) (Elements 89 to 103)

Note: Lanthanides are sometimes excluded when discussing the 3d-series due to their unique properties arising from filling the 4f subshell.

General Electronic Configurations

• d-Block Elements: These elements generally follow the configuration (n-1)d¹-¹ºns² (where n is the principal quantum number).
• f-Block Elements: The configurations are slightly more complex but involve the filling of the f-orbitals in the shell preceding the outermost s and p-orbitals.

Special Cases: Zn, Cd, and Hg (Group IIB)

Zinc (Zn), Cadmium (Cd), and Mercury (Hg) might seem like an exception. In their elemental state, they have completely filled d-orbitals (d¹⁰). However, they are still considered transition metals due to several reasons:

• Complex Formation: They can form complexes with ammonia, halide ions, and amines, showcasing the ability to interact with electron donors through their d-orbitals.
• Chemical Similarities: Their overall chemical behavior aligns more closely with transition metals than with Group IIB (s-block) elements.

Coinage Metals as Transition Metals

Coinage metals (Cu, Ag, and Au) are often classified as transition metals despite having a d¹⁰ configuration in their elemental state. This is because their higher oxidation states (Cu²⁺ ⇒ 3d⁹, Ag²⁺ ⇒ 4d⁹, Au³⁺ ⇒ 5d⁸) have partially filled d-orbitals, allowing them to exhibit characteristic transition metal behavior.

Typical vs. Non-Typical Transition Metals

While most transition metals share common characteristics, there are some exceptions:

Non-Typical Transition Metals

• Group IIB (Zn, Cd, Hg): As discussed earlier, these elements lack partially filled d-orbitals in their ground state and show minimal typical transition metal behavior. Electronic Configuration: ns²(n-1)d¹⁰ (e.g., Zn: 4s²3d¹⁰)

• Group IIIB (Sc, Y, La): Though they have partially filled d-orbitals, their most common oxidation state (M³⁺) results in no d-electrons. This can lead to them exhibiting fewer classic transition metal properties compared to other groups. Electronic Configuration: ns²(n-1)d¹ (e.g., Sc: 4s²3d¹)