Definitions [2]
Define transition metals.
Elements having partially filled d-orbitals in ground state or in excited state are known as transition elements.
Define lanthanoid contraction.
In the lanthanoids, the electrons are filling the 4f-subshell. On moving from left to right, the nuclear charge increases, and this increase is expected to be compensated by the increase in the magnitude of the shielding effect by the 4f-electrons. However, the f-electrons have very poor shielding effects. With an increasing atomic number in the lanthanoid series, there is a progressive decrease in the atomic as well as ionic radii of trivalent ions from La3+ to Lu3+, and this is known as lanthanoid contraction.
Key Points
Key Points: The Actinoids
- Elements in which the last electron enters the 5f-orbital (Th to Lr)
- Second inner transition series (Z = 90 to 103)
- General electronic configuration: \[5f^{1-14},6d^{0-1},7s^{2}\]
- Show irregular electronic configurations
- Stability associated with f⁰, f⁷, f¹⁴ configurations
- Examples of exceptions:
- Am: [Rn] 5f⁷ 7s²
- Cm: [Rn] 5f⁷ 6d¹ 7s²
Concepts [8]
- Position in the Periodic Table - d-block Elements
- Electronic Configurations of the d-block Elements
- General Properties of the Transition Elements (d-block)
- Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
- F-block Elements
- The Lanthanoids
- The Actinoids
- Applications of d and f Block Elements
