(1) (d)-(ii) The incorrect statement among the following is : Actinoids are highly reactive metals, especially when finely divided. (2) Actinoid contraction is greater for element to element than Lanthanoid contraction. (3) Most of the trivalent Lanthanoid ions are colorless in the solid state. (4) Lanthanoids are good conductors of heat and electricity.
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Incorrect statement among the following
Explanation:
- Option(1) is correct. There is increase in surface area, when the actinides are finely divided. The rate of the reaction increases as the more number of molecules of reactant are exposed. That is why, when actinoids are finely divided they are highly reactive metals.
- Option(2) is correct. Shielding effect of 5f(actinoids) orbitals are very poor than 4f(lanthanoids) orbitals. Therefore, in case of actinoids effective nuclear charge experienced by outermost shell is much larger than that experienced by lanthanoids. Therefore, Actinoid contraction is greater than that of lanthanoid contraction.
- Option(3) is incorrect as many of the trivalent lanthanoid ions are coloured in solid state as well as in aqueous state due to the presence of free electron in 5f orbital. Therefore, Option(3) is incorrect.
- Option(4) is correct as lanthanoids can conduct heat and electricity. Therefore, lanthanoids are good conductor of heat and electricity.
So, Option (3) is incorrect.
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