A metallic element crystallizes into a lattice containing a sequence of layers ABABAB....Any packing of spheres leaves out voids in the lattice. What percentage by volume of this lattice is empty space? ( IIT-.IEF 2006)

The sequence ABABAB... indicates hcp unit cell. Now, there are 6 atoms per unit cell and volume of the umt cell is 24√2 r3.Thus, the packing fraction is:

The coordination number of Al in the crystalline state of AlCl3 is .... (IIT-JEE 2009)

AlCl3 exist in CCP unit cell with 6 co-ordinate layer structure and coordination number of Al is (6)

The number of hexagonal faces that are present in truncated octahedron is .... (IIT-JEE 2011)

The number of hexagonal faces that are present in truncated octahedron is  (6) this can seen if given fig.

In Diamond Carbon atom occupie FCC lattice point as well as alternate tetrahedral voids. If edge length of unit cell is 3.56 pm the find the radius of carbon atom is.

What are structural information of Dimomd ?

Diamond structure is ZnS type structure  in which carbon atoms forms  a face centred cubic (FCC/CCP) lattice as well as  four out of eight (50%) or alternate tetrahedral voids are occupied by carbon atoms. Every atom in this structure is surrounded tetrahedrally by four other. No discrete molecule can be discerned (identified) in diamond .the entire crystal is giant molecule a unit cell of which is shown as below.

Note : Only those atoms which form four covalent bond produce a repeated 3D structure using only covalent bonds.

Lattice of Diamond is ZnS type structure.

(1) C- form FCC/CCP (4-atoms)

(2) C- atoms present at the (50%) alternative tetrahedral voids (4-atoms)

(3) Total Number of one lattice unit is eight (8) hence molecular formula of diamond is (C8) (i.e. Z= 8)

(4) Number of C-C bond in lattice cell is = 4×4= 16

(5) Number of C-C bond per carbon atom is 16/8=2

(6) The distance between two Corbin atom is d_C-C = a√3/4 and the radius of carbon atom = dc-c/2 = r_c = a√3/2x4

(8) Packing efficiency (PE = π√3/10= 0.34 or 34%):

(9) Voids = 66 % 

Additional Information: 

Related Questions:

What are the normal spinel structures?

What are the inverse spinel structures?

How to calculate radius ratio of square Voids?

How to calculate radius ratio triangular voids?

How to calculate packing fraction or packing efficiency of two dimensional (2D) hexagonal packing solid atoms?

The coordination number of Al in the crystalline state of AlCl3 is .... (IIT-JEE 2009)

The number of hexagonal faces that are present in truncated octahedron is .... (IIT-JEE 2011)

What are structural information of Dimomd ?

In diamond, carbon atoms occupy FCC/CCP lattice point as well as alternate tetrahedral voids. If edge length of unit cell is 3.56pm, the radius of carbon atom is ?

The edge length of unit cubic cell of diamond is 356.7 pm and this cubic unit cell contains 8 carbon atoms calculate (A) Distance between two carbon atoms, assuming them to spheres in contact (B) Radius of carbon atoms (C) Fraction of the total volume that is occupied by the carbon atoms.