Transition and Inner Transition Elements

d-Block Elements:

• Elements in which the last electron enters (n−1)d orbital.
• Located in the middle of the periodic table.
• Also called transition elements.
• Show variable oxidation states, colored compounds, complex formation.

General Electronic Configuration: \[(n-1)d^{1-10}ns^{0-2}\]

f-Block Elements:

• Elements in which the last electron enters (n−2)f orbital.
• Placed separately at the bottom of the periodic table.
• Known as inner transition elements.

Two series:

• Lanthanides (4f): Ce (58) → Lu (71)
• Actinides (5f): Th (90) → Lr (103)

General Electronic Configuration: \[(n-2)f^{1-14}(n-1)d^{0-1}ns^{2}\]