Definitions [1]
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
Important Questions [15]
- What Are F-block Elements?
- Define lanthanoid contraction.
- What Are Chemical Twins? Write ‘Two’ Examples.
- What are lanthanoids?
- Which among the following pairs of elements is 'not' an example of chemical twins?
- Write the Different Oxidation States of Iron
- Explain, why lanthanum (Z = 57) forms La3+ ion, while cerium (Z = 58) forms Ce4+ ion?
- What is Lanthanoid contraction?
- What are the consequences of lanthanoid contraction?
- Explain the cause of Lanthanoids contraction.
- What is the Action of the Following on Lanthanoids? A. Water B. Sulphur, Heat C. Nitrogen, Heat
- Explain effects of lanthanoid contraction.
- Write Four Points of Distinction Between Lanthanoids and Actinoids.
- What is the Position of Actinoids in Periodic Table ?
- Distinguish between lanthanoid and actinoids.
