Because of lanthanoid contraction, which of the following pairs of elements have nearly same atomic radii? (Numbers in the parenthesis are atomic numbers)

Question

Which is the inner transition element of the following?

Answer 1

The question requires identifying which pair of elements among the given options have nearly the same atomic radii due to the phenomenon known as the "lanthanoid contraction."

Concept Explanation: Lanthanoid contraction refers to the steady decrease in the size of the lanthanoid series elements (from Lanthanum (La) to Lutetium (Lu)) as we move across the series. This contraction is attributed to the poor shielding effect offered by the f-orbital electrons. As a result, the outer electrons are pulled closer to the nucleus, leading to a smaller atomic and ionic radius. This contraction also affects the elements that come after the lanthanoid series in the periodic table, making them similar in size to the elements preceding the lanthanoids.

In particular, below the lanthanoids, elements such as Hafnium (Hf) and Zirconium (Zr) exhibit nearly identical atomic radii. Though Zr comes much earlier in the periodic table than Hf, because of the lanthanoid contraction between them, both elements end up having a similar size. This makes Hf's atomic radius similar to Zr's even though there are several more protons in Hf's nucleus.

Analysis of Options:

Zr (40) and Hf (72): Due to lanthanoid contraction, Hf has almost the same atomic radius as Zr, despite having more protons. Therefore, this pair has nearly the same atomic radii.
Zr (40) and Ta (73): Tantalum (Ta) follows Hf and does not have the same atomic radius as Zr because further down the periodic table, the effect of lanthanoid contraction does not match Zr's radius.
Ti (22) and Zr (40): Titanium (Ti) and Zirconium (Zr) do not exhibit similar atomic radii since they belong to different periods, and Ti does not experience the effects caused by the lanthanoid contraction.
Zr (40) and Nb (41): Niobium (Nb) and Zirconium (Zr) are consecutive elements, but they do not have the same atomic radius due to the absence of lanthanoid contraction effects between them.

Thus, the correct answer is Zr (40) and Hf (72).

Answer 2

The question requires identifying which pair of elements among the given options have nearly the same atomic radii due to the phenomenon known as the "lanthanoid contraction."

Concept Explanation: Lanthanoid contraction refers to the steady decrease in the size of the lanthanoid series elements (from Lanthanum (La) to Lutetium (Lu)) as we move across the series. This contraction is attributed to the poor shielding effect offered by the f-orbital electrons. As a result, the outer electrons are pulled closer to the nucleus, leading to a smaller atomic and ionic radius. This contraction also affects the elements that come after the lanthanoid series in the periodic table, making them similar in size to the elements preceding the lanthanoids.

In particular, below the lanthanoids, elements such as Hafnium (Hf) and Zirconium (Zr) exhibit nearly identical atomic radii. Though Zr comes much earlier in the periodic table than Hf, because of the lanthanoid contraction between them, both elements end up having a similar size. This makes Hf's atomic radius similar to Zr's even though there are several more protons in Hf's nucleus.

Analysis of Options:

Zr (40) and Hf (72): Due to lanthanoid contraction, Hf has almost the same atomic radius as Zr, despite having more protons. Therefore, this pair has nearly the same atomic radii.
Zr (40) and Ta (73): Tantalum (Ta) follows Hf and does not have the same atomic radius as Zr because further down the periodic table, the effect of lanthanoid contraction does not match Zr's radius.
Ti (22) and Zr (40): Titanium (Ti) and Zirconium (Zr) do not exhibit similar atomic radii since they belong to different periods, and Ti does not experience the effects caused by the lanthanoid contraction.
Zr (40) and Nb (41): Niobium (Nb) and Zirconium (Zr) are consecutive elements, but they do not have the same atomic radius due to the absence of lanthanoid contraction effects between them.

Thus, the correct answer is Zr (40) and Hf (72).

Because of lanthanoid contraction, which of the following pairs of elements have nearly same atomic radii? (Numbers in the parenthesis are atomic numbers)

The Correct Option is A

Solution and Explanation

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