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The d-And-f-Block Elements
Question
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Why La, Gd and Lu has low value of 3rd ionisation enthalpies?

Answer

The electronic configuration of lanthanum is 4f0 5d1 6s2, electronic configuration of Gadolinium is 4f7 5d1 6s2 and electronic configuration of Lutetium 4f14 5d1 6s2. The lanthanum (La), gadolium (Gd) and Lutetium (Lu) acquires empty, half filled and fully filled 4f subshell respectively in their M3+ state and due to the exchange enthalpy, this state acquires extra-stability and they have low 3rd ionisation enthalpy.

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Some More Questions From The d-And-f-Block Elements Chapter

Explain why Cu+ ion is not stable in aqueous solutions?

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?

The outer electronic configuration of copper is 3d10 4s1, yet it is considered transition element. Why?

Why the melting points of transition elements are high?

Why Zn, Cd and Hg are not regarded as transition elements?

Name the first element of 3rd transition series.

Though copper, silver and gold have completely filled sets of d-orbitals yet they are considered as transition metals. Why?

Why are transition elements so named?

Why are transition elements known as d-block elements?