Close Packing

Q. Taking the reference to be the corner particles for a fcc lattice, the number of second nearest atoms and the distance between them is, respectively :
Here,
r is the radius of the atom

Q. In a ccp structure, a cube is formed by joining the centres of all the tetrahedral voids to generate a new cube. Then, the new cube would contain:

1. 1 full octahedral void only
2. 1 full tetrahedral void only
3. 8 full tetrahedral voids and 1 full octahedral void
4. 1 full tetrahedral void, 1 full octahedral void

Q. Copper crystallises in a structure of face centered cubic unit cell. The atomic radius of copper is $1.28$$A^{\circ }$. What is edge length of the unit cell?

1. $3.94A^{\circ }$
2. $4.15A^{\circ }$
3. $2.16A^{\circ }$
4. $3.62A^{\circ }$

Q. Which of the following unit cell represent the first nearest atom distance in fcc?

1. 
2. 
3. 
   
   
4. 

Q. What is the distinguishing layer between hexagonal close packing and cubic close packing?

Q. In a face centered lattice of X and Y, X atoms are present at the corners while Y atoms are at face centers. What would be the simplest formula of the compound if one of the X atoms is missing from a corner in each unit cell?

Q. Stacking of square packed layers/sheets exactly above one another gives

Q. Identical spheres undergo two-dimensional packing to give square close packing (scp) and hexagonal close packing (hcp). Which of the following statements is correct?

1. The centres of the neighboring spheres in hcp join to form a hexagon
2. The centres of the neighboring spheres in scp form a simple cubic structure
3. The ratio of coordination number for a sphere in scp to that of hcp is 1 : 3
4. The ratio of coordination number for a sphere in scp to that of hcp is 3 : 2

Q. The coordination number for a ccp lattice is :

Q. Element A has a face centred unit cell in which A is absent from half of the face centres. The packing fraction is $\frac{x\times \sqrt{2}\pi }{96}$.
The value of x is

1. 3.33
2. 5
3. 7.45
4. 10

Q. Choose the correct statement for 3-D hexagonal closed packing :

Q.

What do we mean by close packed structure?

1. The particles in the crystal are differently arranged.

2. The particles in the crystal are less in number.

3. The particles in the crystal arrange themselves with least vacant space.

4. The particles in the crystal are dense.

Q. Choose the correct statement regarding cubic close packing.

1. Cubic close packing gives fcc structure
2. Fourth layer is identical to the second layer
3. Cubic close packing gives bcc structure
4. Fourth layer is not identical to the first layer

Q. Total number of particles i.e. $\left(Z_{eff}\right)$ in a 3-D hexagonal close packed (hcp) unit cell is

Q. What will be the coordination number of cubic close packing (ccp) lattice?

Q. In chromium (III) chloride, $\left(CrC{l}_3\right)$, chloride ions have cubic close packed arrangement and $Cr\left(III\right)$ ions are present in octahedral voids.
Choose the correct option(s):

1. $\text{Fraction of total voids occupied}=\frac{1}{6}$
2. $\text{Fraction of total voids occupied}=\frac{1}{9}$
3. $\text{Fraction of octahedral voids occupied}=\frac{1}{3}$
4. $\text{Fraction of octahedral voids occupied}=\frac{1}{2}$

Q. $Zn$ when converted from its melted state to its solid state, it has HCP structure, then find out no. of nearest atom:-
AIPMT-2001

Q. The ABAB.. type packing and ABCABC.. type packing are respectively called as:

Q. In a simple cubic lattice of anions, the side length of the unit cell is $3.0\stackrel{o}{A}.$ The diameter of the void in the body centre is

Q. Which of the following figure represent the tetrahedral void?
(note: red spheres are placed over the layer of black spheres)

1. 
2. 
3. 
4. 

Q.

A substance $A_x{B}_y$ crystallizes in a face - centred cubic lattice in which atoms A occupy the centres of each face of the cube. Identify the correct composition of the substance $A_x{B}_y$.

1. $A{B}_3$

2. $A_4{B}_3$

3. $A_{3}B$

4. Cannot be specified

Q. In a binary compound, atoms of element A form a hcp structure and those of elements $M$ occupy $2/3$ of the tetrahedral voids of the hcp structure. The formula of the binary compound is:

Q. Hexagonal close packed arrangement of ions is described as

1. ABC ABA
2. ABC ABC
3. ABABA
4. ABBAB

Q.

In a face-centred cubic lattice, atom A occupies the corner position and atom B occupies the face -centred positions. If one atom of B is missing from one of the face - centred points, the formula of the compound is

1. $A_2{B}_5$

2. $A_{2}B$

3. $A{B}_2$

4. $A_2{B}_2$

Q. If the separation between the $1^{st}$ the $5^{th}$ layer in an ABCABC type crystal is $n\sqrt{\frac{2}{27}}r$ (r = radius of atom), then n is

Q.

In a face-centred cubic lattice, atom A occupies the corner position and atom B occupies the face -centred positions. If one atom of B is missing from one of the face - centred points, the formula of the compound is

1. $A_2{B}_5$

2. $A_{2}B$

3. $A{B}_2$

4. $A_2{B}_2$

Q.

The close packing arrangement of ABCABC in 3-D refers to which of the following?

1. Primitive Cubic Close packing

2. Body-centre Cubic Close packing

3. Face-centre Cubic Close packing

4. Hexagonal Close Packing

Q. For a cubic crystal structure which one of the following relations indicating the cell characteristics is correct:
AIMPT -2007

1. $a=b=c$ and $\alpha \ne \beta \ne \gamma ={90}^0$
2. $a\ne b\ne c$ and $\alpha \ne \beta and\gamma \ne {90}^0$
3. $a=b=c$ and $\alpha =\beta =\gamma ={90}^0$
4. $a\ne b\ne c$ and $\alpha =\beta =\gamma ={90}^0$

Q. The correct statement(s) for cubic close packed (ccp) three dimensional structure is/are:

1. The number of the nearest neighbours for an atom present in the topmost layer is 12.
   
2. The efficiency of atom packing is 74%.
3. The number of octahedral and tetrahedral voids per atom are 1 and 2, respectively.
4. The unit cell edge length is $2\sqrt{2}$ times the radius of the atom.

Q. In a face centerd lattice of $X$ and $Y,X$ atoms are present at the corners while $Y$ atoms are at face centers. Then, the formula of the compound would be if one of the $X$ atoms is missing from a corner in each unit cell:

1. $X_7{Y}_{24}$
2. $X_{24}{Y}_7$
3. $X{Y}_{24}$
4. $X_{24}Y$