Ncert Exercises & Solutions

Select the correct option based on statements below:

Assertion (A):	The packing efficiency is maximum for the fcc structure.
Reason (R):	The coordination number is 12 in fcc structure.

1.	Both (A) and (R) are true and (R) is the correct explanation of (A).
2.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
3.	(A) is true but (R) is false.
4.	(A) is false but (R) is true.

Hint: The paxking efficiency in FCC is 74%

Packing efficiency is maximum for fcc structure because it consists of total four atoms per unit cell. Packing efficiency is

maximum in fcc structure which is equal to 74%. The coordination number is 12 in fcc structures.

Hence, Assertion and Reason both are correct statements but Reason is not correct explanation for Assertion.