Question

The lattice of \(MH_{2.55}\) is different from the lattice of \(M\). What is \(M\)?

• A. Ac
• B. Yb
• C. Pd
• D. Ce

Hint:

Hydride formation in rare earth metals like Yb often results in significant changes in material properties, including electrical and structural characteristics, due to the altered lattice structure.

Answer 1

The Correct Option is B

Step 1: Consider the properties of Yb in forming hydrides. Ytterbium (Yb), as a rare earth element, is known to form complex metal hydrides that can display various hydrogen stoichiometries. The lattice structure of these hydrides can significantly differ from that of the pure metal due to the insertion of hydrogen atoms into the metal lattice. 
Step 2: Understand the impact of hydrogen on metal lattices. When Yb absorbs hydrogen, it forms hydrides where the hydrogen atoms occupy interstitial sites within the Yb lattice. This can lead to an expansion and distortion of the lattice, which significantly changes the crystal structure from that of the metallic phase. 
Step 3: Implications for \(MH_{2.55}\). Given that \(MH_{2.55}\) for Yb suggests a high hydrogen content relative to ytterbium, the hydride lattice is likely to be different from the lattice of pure Yb due to these interstitial hydrogen atoms causing lattice expansion and potentially new crystallographic phases.