Question

Identify the correct sets of inner transition elements. \[ \text{I. } \mathrm{Nb,\ W,\ Sg} \] \[ \text{II. } \mathrm{Hs,\ Mt,\ Ds} \] \[ \text{III. } \mathrm{Tb,\ Dy,\ Cf} \] \[ \text{IV. } \mathrm{Nd,\ Bk,\ Es} \] The correct answer is (only):

• A. II, III, IV only
• B. III, IV only
• C. I, II, IV only
• D. I, II, III only

Hint:

All lanthanoids and actinoids belong to the \(f\)-block and are called inner transition elements. Any set containing only \(f\)-block elements is correct.

Answer 1

The Correct Option is B

Concept: Inner transition elements are the \(f\)-block elements of the periodic table. They consist of:
• Lanthanoids \((58-71)\)
• Actinoids \((90-103)\) These elements involve filling of \(4f\) or \(5f\) orbitals.

Step 1: Examine Set I. \[ \mathrm{Nb,\ W,\ Sg} \] Niobium (\(\mathrm{Nb}\)), Tungsten (\(\mathrm{W}\)) and Seaborgium (\(\mathrm{Sg}\)) belong to the \(d\)-block. These are transition elements and not inner transition elements. Hence Set I is incorrect.

Step 2: Examine Set II. \[ \mathrm{Hs,\ Mt,\ Ds} \] Hassium, Meitnerium and Darmstadtium are also \(d\)-block transition metals. Therefore Set II is incorrect.

Step 3: Examine Set III. \[ \mathrm{Tb,\ Dy,\ Cf} \] Terbium and Dysprosium are lanthanoids. Californium is an actinoid. All belong to the \(f\)-block. Hence Set III is correct.

Step 4: Examine Set IV. \[ \mathrm{Nd,\ Bk,\ Es} \] Neodymium is a lanthanoid. Berkelium and Einsteinium are actinoids. All are inner transition elements. Hence Set IV is correct. Therefore the correct combination is \[ \boxed{\text{III and IV only}} \]