Advertisements
Advertisements
प्रश्न
What is lanthanoid contraction and what are the effects of lanthanoid contraction?
Advertisements
उत्तर
As we move across the 4f series, the atomic and ionic radii of lanthanoids show a gradual decrease with an increase in atomic number. This decrease in ionic size is called lanthanoid contraction.
Effects or Consequences of lanthanoid contraction:
1. Basicity differences: As we move from Ce3+ to Lu3+, the basic character of Ln3+ ions decreases. Due to the decrease in the size of Ln3+ ions, the ionic character of the Ln – OH bond decreases (covalent character increases) which results in a decrease in the basicity.
2. Similarities among lanthanoids: In the complete f-series only a 10 pm decrease in atomic radii and a 20 pm decrease in ionic radii are observed. Because of this very small change in radii of lanthanoids, their chemical properties are quite similar.
The elements of the second and third transition series resemble each other more closely than the elements of the first and second transition series due to lanthanoid contraction.
For example,
- 4d series – Zr – Atomic radius 145 pm
- 5d series – Hf – Atomic radius 144 pm
APPEARS IN
संबंधित प्रश्न
Write the general outer electronic configuration of f- block elements.
Which one of the following statements related to lanthanons is incorrect?
Which of the following oxidation states is most common among the lanthanoids?
The most common oxidation state of actinoids is ____________.
Justify the position of lanthanides and actinides in the periodic table.
Out of Lu(OH)3 and La(OH)3 which is more basic and why?
Which of the following is not an actinoid?
In the modern periodic table, elements are arranged in order of increasing atomic numbers which is related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four blocks, viz, s, p, d and f. The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Arfbau principle, the seven periods have 2, 8, 8, 18, 18, 32 and 32 elements respectively. The seventh period is still incomplete. To avoid the periodic table being too long, the two series of f-block elements, called lanthanoids and actinoids are placed at the bottom of the main body of the periodic table.
Which of the elements whose atomic numbers are given below, cannot be accommodated in the present set-up of the long form of the periodic table?
Illustrate by taking examples of transition elements and non-transition elements that oxidation states of elements are largely based on electronic configuration.
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:
Assertion A: Size of Bk3+ ion is less than Np3+ ion.
Reason R: The above is a consequence of the lanthanoid contraction.
In the light of the above statements, choose the correct answer from the options given below.
