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NEETChemistryd and f Block Elements

Which of the following pairs of elements exhibits almost identical atomic radii as a direct consequence of lanthanoid contraction?

Options

  1. ANb and Ta
  2. BTi and Zr
  3. CY and La
  4. DLi and Mg

Correct answer

A. Nb and Ta

Step-by-step solution

Due to lanthanoid contraction, the atomic radii of the elements of the 5d transition series are very similar to those of the corresponding elements of the 4d series. This effect is observed from Group 4 onwards because the filling of 4f orbitals occurs after Lanthanum ( La , Z=57 ). Therefore, Niobium ( Nb , 4d series) and Tantalum ( Ta , 5d series) have almost identical atomic radii. The pair Y and La (Group 3) does not show this effect as La precedes the 4f series. Ti and Zr are 3d and 4d elements respectively, a

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