Question

The solid having the least packing efficiency is _ _ _.

• A. caesium chloride
• B. cadmium iodide
• C. zinc sulfide (wurtzite form)
• D. zinc sulfide (zinc blende form)

Hint:

Close-packed structures (FCC/HCP) have highest packing efficiency (~74\%), while BCC-type structures have lower (~68\%)

Answer 1

The Correct Option is A

Step 1: Idea of packing efficiency.
Close packed solids fill about 74 percent of space, while a body centred type fills about 68 percent.

Step 2: Classify the solids.
Both zinc sulfide forms and cadmium iodide are built on close packing, so they pack well. Caesium chloride uses a body centred type arrangement.

Step 3: Pick the lowest.
Caesium chloride has the least packing efficiency of the group.

Step 4: Answer.
\[ \boxed{\text{caesium chloride}} \]