Match the type of packing given in Column I with the items given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Square close packing in two dimensions | 1. | Triangular voids |
| B. | Hexagonal close packing in two dimensions | 2. | Pattern of spheres is repeated in every fourth layer |
| C. | Hexagonal close packing in three dimensions | 3. | Coordination number = 4 |
| D. | Cubic close packing in three dimensions | 4. | Pattern of sphere is repeated in alternate layers |
A. $\rightarrow(3)$ B. $\rightarrow$ (1) C. $\rightarrow$ (4) D. $\rightarrow$ (2)
A. Square close packing in two dimensions each sphere have coordination number 4, as shown below
B. Hexagonal close packing in two dimensions each sphere have coordination number 6 as shown below and creates a triangular void
C. Hexagonal close packing in 3 dimensions is a repeated pattern of sphere in alternate layers also known as $A B A B$ pattern
D. Cubic close packing in a 3 dimensions is a repeating pattern of sphere in every fourth layer
Assertion (A) The total number of atoms present in a simple cubic unit cell is one.
Reason (R) Simple cubic unit cell has atoms at its corners, each of which is shared between eight adjacent unit cells.
Assertion (A) Graphite is a good conductor of electricity however diamond belongs to the category of insulators.
Reason (R) Graphite is soft in nature on the other hand diamond is very hard and brittle.
Assertion (A) Total number of octahedral voids present in unit cell of cubic close packing including the one that is present at the body centre, is four.
Reason (R) Besides the body centre there is one octahedral void present at the centre of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.
Assertion (A) The packing efficiency is maximum for the fcc structure.
Reason (R) The coordination number is 12 in fcc structures.