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प्रश्न
What is lanthanoid contraction and what are the effects of lanthanoid contraction?
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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
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संबंधित प्रश्न
Which of the following lanthanoid ions is diamagnetic?
Assertion: Ce4+ is used as an oxidizing agent in volumetric analysis.
Reason: Ce4+ has the tendency of attaining +3 oxidation state.
The most common oxidation state of actinoids is ____________.
The actinoid elements which show the highest oxidation state of +7 are ____________.
Which one of the following is not correct?
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?
The elements in which electrons are progressively filled in 4f-orbital are called ______.
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?
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.
The elements with atomic numbers 35, 53 and 85 are all ______.
