Advertisements
Advertisements
प्रश्न
What is Lanthanoid contraction?
What do you understand by lanthanoid contraction?
What is lanthanoid contraction? Explain.
What is meant by Lanthanide contraction?
Advertisements
उत्तर १
The lanthanide series of elements is defined as a gradual reduction in atom size, known as lanthanoid contraction. This reduction occurs due to insufficient shielding of additional electrons in the 4f subshell by filled 5s and 5p orbitals. As a result, the effective nuclear charge increases, resulting in smaller atomic sizes.
उत्तर २
- The size of the atoms and ions has been found to routinely decrease as one moves from cerium to lutetium. In the case of tripositive ions, this size reduction is more consistent.
- The nuclear charge rises with atomic number when one transitions from Ce to Lu, and the inner 4f-orbital gains the differentiating electron.
- The shielding of one 4f-electron by another from growing nuclear charge is imperfect due to the irregular geometries of 4f-orbitals.
- As a result, each 4f-electron experiences an increasing effective nuclear charge as the atomic number rises. As each electron in the 4f-subshell is added, the size is somewhat decreased.
- As a result, the size steadily contracts as the effective nuclear charge steadily rises with each additional electron in the 4f-subshell.
- Lanthanoid contraction refers to the cumulative effect of successive contractions on all lanthanoids.
- The total contraction in atomic radius in going from Ce to Lu is about 15 pm.
- Atomic radii show a tendency to decrease in size; however, the pattern is irregular.
Notes
Students can refer to the provided solutions based on their preferred marks.
APPEARS IN
संबंधित प्रश्न
What are chemical twins? Write ‘two’ examples.
Account for the following :
Zr and Hf have almost similar atomic radii.
Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.
What are the different oxidation states exhibited by the lanthanoids?
Compare the chemistry of actinoids with that of the lanthanoids with special reference to atomic and ionic sizes.
Compare the chemistry of actinoids with that of the lanthanoids with special reference to chemical reactivity.
The chemistry of the actinoid elements is not so smooth as that of the Lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.
Write the electronic configurations of the element with the atomic number 61.
Write the different oxidation states of iron
Explain effects of lanthanoid contraction.
What are the consequences of lanthanoid contraction?
Account for the following:
Zn, Cd and Hg are soft metals.
Explain the cause of Lanthanoids contraction.
Which trivalent ion has the maximum size in the Lanthanoid series, i.e., Lanthanum ion (La3+) to Luteium ion (Lu3+)?
(at. no. of Lanthanum = 57 and Lutetium = 71)
Name an element of lanthanoid series which is well knwon to shown +4 oxidation state. Is it a strong oxidising agent or reducing agent?
What is meant by Lanthanide contraction? Write the general electronic configuration of inner transition elements.
What is the action of the following on lanthanoids?
a. water
b. Sulphur, heat
c. nitrogen, heat
The f-block elements are known as ____________.
General electronic configuration of actinoids is `(n-2)f^(1-14)(n - 1)d^(0-2)ns^2`.Which of the following actinoids have one electron in 6d orbital?
(i) U (Atomic no. 92)
(ii) Np (Atomic no.93)
(iii) Pu (Atomic no. 94)
(iv) Am (Atomic no. 95)
Although +3 is the characteristic oxidation state for lanthanoids but cerium also shows +4 oxidation state because:
(i) it has variable ionisation enthalpy
(ii) it has a tendency to attain noble gas configuration
(iii) it has a tendency to attain f 0 configuration
(iv) it resembles Pb4+
Although Zr belongs to 4d and Hf belongs to 5d transition series but it is quite difficult to separate them. Why?
Although +3 oxidation states is the characteristic oxidation state of lanthanoids but cerium shows +4 oxidation state also. Why?
Match the property given in Column I with the element given in Column II.
| Column I (Property) | Column II (Element) | |
| (i) | Lanthanoid which shows +4 oxidation state |
(a) Pm |
| (ii) | Lanthanoid which can show +2 oxidation state |
(b) Ce |
| (iii) | Radioactive lanthanoid | (c) Lu |
| (iv) | Lanthanoid which has 4f7 electronic configuration in +3 oxidation state |
(d) Eu |
| (v) | Lanthanoid which has 4f14 electronic configuration in +3 oxidation state |
(e) Gd |
| (f) Dy |
On the basis of Lanthanoid contraction, explain the following:
Nature of bonding in \[\ce{La2O3}\] and \[\ce{Lu2O3}\] .
On the basis of Lanthanoid contraction, explain the following:
Stability of the complexes of lanthanoids.
On the basis of Lanthanoid contraction, explain the following:
Trends in acidic character of lanthanoid oxides.
Which of the following pairs has the same ionic size?
In lanthanoid the last electron enters (n - 2)f subshell where n is equal to ______.
Zr (Z = 40) and Hf (Z = 72) have similar atomic and ionic radii because of ______.
Which one of the lanthanoids given below is the most stable in divalent form?
Mischmetal is an alloy consisting mainly of ______.
Trivalent Lanthanoid ions such as La3+ (Z = 57) and Lu3+ (Z = 71) do not show any colour in their solution. Give a reason.
Name an important alloy which contains some of the lanthanoid metals.
The pair of lanthanoid ions which are diamagnetic is:
