Question

Question No. 11
Among the lanthanides Eu, Tb, Er and Dy, which one readily forms stable divalent ions?​

Answer 1

Answer:

The informal chemical symbol Ln is used in general discussions of lanthanide chemistry to refer to any lanthanide. All but one of the lanthanides are f-block elements, corresponding to the filling of the 4f electron shell; depending on the source, either lanthanum or lutetium is considered a d-block element, but is included due to its chemical similarities with the other 14.[5] All lanthanide elements form trivalent cations, Ln3+, whose chemistry is largely determined by the ionic radius, which decreases steadily from lanthanum to lutetium.

They are called lanthanides because the elements in the series are chemically similar to lanthanum. Both lanthanum and lutetium have been labeled as group 3 elements, because they have a single valence electron in the 5d shell. However, both elements are often included in discussions of the chemistry of lanthanide elements. Lanthanum is the more often omitted of the two, because its placement as a group 3 element is somewhat more common in texts and for semantic reasons: since "lanthanide" means "like lanthanum", it has been argued that lanthanum cannot logically be a lanthanide, but IUPAC acknowledges its inclusion based on common usage.[6]

In presentations of the periodic table, the lanthanides and the actinides are customarily shown as two additional rows below the main body of the table,[2] with placeholders or else a selected single element of each series (either lanthanum and actinium, or lutetium and lawrencium) shown in a single cell of the main table, between barium and hafnium, and radium and rutherfordium, respectively. This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the lanthanide and actinide series in their proper places, as parts of the table's sixth and seventh rows (periods).

Explanation:

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Answer 2

Among the lanthanides Eu is the one readily forms which stable divalent ions.

Explanation for the answer:

• The Correct option is Eu.
• We know that the Electronic configuration of Europium is 4f⁷6s².
• Therefore, the state which is most stable divalent for Eu is +2.
• As this causes or lead to a half filled electronic shell, this state would be stable divalent.

Explanation for the Incorrect answers:

• Eu [xe] 4f¹6s²
• Tb [xe] 4f⁹6s²
• Dy [xe] 4f¹⁰