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NEET CHEMISTRYThe d-and f-Block ElementsMedium

Question

The decrease in size from left to right in the actinoid series is greater and more gradual than that in the lanthanoid series due to:

A

4f4f orbitals are penultimate

B

4f4f orbitals have a greater shielding effect

C

5f5f orbitals have a poor shielding effect

D

5f5f orbitals have a greater shielding effect

Step-by-Step Solution

Similar to the lanthanoids, actinoids exhibit a gradual decrease in the size of their atoms or M3+M^{3+} ions across the series, a phenomenon known as actinoid contraction. However, the contraction is greater from element to element in the actinoid series compared to the lanthanoid series. This occurs because the 5f5f electrons provide poorer shielding from the increasing nuclear charge than the 4f4f electrons . As a result, the outer electrons are pulled more strongly towards the nucleus, leading to a greater decrease in atomic and ionic sizes.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from The d-and f-Block Elements. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYThe d-and f-Block Elementsdecreaseactinoidseriesgreatergradual

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A.$d^5$ to $d^2$ configuration
B.$d^4$ to $d^5$ configuration
C.$d^3$ to $d^5$ configuration
D.$d^5$ to $d^4$ configuration
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The catalytic activity of transition metals is due to:

A.High enthalpy of atomization
B.Paramagnetic behaviour
C.Colour of hydrated ions
D.Variable oxidation states
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The manganate and permanganate ions are tetrahedral, due to:

A.The π-bonding involves the overlap of d-orbitals of oxygen with d-orbitals of manganese.
B.The π-bonding involves the overlap of p-orbitals of oxygen with d-orbitals of manganese.
C.Absence of π-bonding.
D.The π-bonding involves the overlap of p-orbitals of oxygen with p-orbitals of manganese.
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The incorrect statement among the following is:

A.Lanthanoids are good conductors of heat and electricity.
B.Actinoids are highly reactive metals, especially when finely divided.
C.Actinoid contraction is greater for element to element than Lanthanoid contraction.
D.Most of the trivalent Lanthanoid ions are colourless in the solid-state.
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When neutral or faintly alkaline $KMnO_4$ is treated with potassium iodide, iodide ion is converted into 'X'. 'X' is:

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C.$IO_3^-$
D.$IO^-$
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Identify the incorrect statement among the following:

A.There is a decrease in the radii of the atoms or ions as one proceeds from $\text{La}$ to $\text{Lu}$.
B.Lanthanoid contraction is the accumulation of successive shrinkages.
C.As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of elements.
D.Shielding power of 4f electrons is quite weak.
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Acidified $K_2Cr_2O_7$ solution turns green when $Na_2SO_3$ is added to it. This is due to the formation of:

A.$CrO_4^{2-}$
B.$Cr_2(SO_3)_3$
C.$CrSO_4$
D.$Cr_2(SO_4)_3$
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Which of the following ions will exhibit colour in aqueous solutions?

A.$La^{3+} (Z=57)$
B.$Ti^{3+} (Z=22)$
C.$Lu^{3+} (Z=71)$
D.$Sc^{3+} (Z=21)$
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