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NEET CHEMISTRYThe d-and f-Block ElementsMedium

Question

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.

Step-by-Step Solution

Let us evaluate all the given statements:

  1. Statement 1 is correct: Lanthanoids are silvery-white soft metals. They possess typical metallic structures and are good conductors of heat and electricity .
  2. Statement 2 is correct: Actinoids are highly reactive metals, particularly when they are in a finely divided state .
  3. Statement 3 is correct: The actinoid contraction is greater from element to element than the lanthanoid contraction. This occurs because the 5f5f electrons provide poorer shielding from the increasing nuclear charge compared to the 4f4f electrons .
  4. Statement 4 is incorrect: Many trivalent lanthanoid ions are actually coloured, both in the solid state and in aqueous solutions. This colour is primarily attributed to the presence of ff electrons, which allow for ff-ff electronic transitions .

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 Elementsincorrectstatementfollowing

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The $E^\circ$ value for the $Mn^{3+}/Mn^{2+}$ couple is more positive than that of $Cr^{3+}/Cr^{2+}$ or $Fe^{3+}/Fe^{2+}$ due to change of:

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
EasySolve

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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When neutral or faintly alkaline $KMnO_4$ is treated with potassium iodide, iodide ion is converted into 'X'. 'X' is:

A.$I_2$
B.$IO_4^-$
C.$IO_3^-$
D.$IO^-$
MediumSolve

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.$Cr_2(SO_4)_3$
MediumSolve

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.$Sc^{3+} (Z=21)$
EasySolve

Which of the following ions displays the d-d transition and paramagnetism?

A.$\text{CrO}_4^{2-}$
B.$\text{Cr}_2\text{O}_7^{2-}$
C.$\text{MnO}_4^-$
D.$\text{MnO}_4^{2-}$
MediumSolve

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