Question

1. The ionic radii of Na+ and Cl" are 95 pm and 181 pm respectively. What is the edge length of
the unit cell of NaCl ?
(1) 276 pm
(2) 552 pm
(3) 362 pm
0 (4) 457 pm
2. The ratio of cationic radius to anionic radius in ionic crystal of compound AB is greater than
0.732. The crystal coordination number of cation is :
(1) 4
(2) 6
(3) 8
(4) 12
3. The crystal coordination number of Zn2+ in Zinc blend (ZnS) is :
(1) 4
(2) 6
(3) 8
(4) 12
4. The number of Na+ ions in the unit cell of NaCl is :
(1) 1
0 (2) 2
(3) 3
(4) 4
5. The coordination number of Nain NaCl crystals is :
(1) 4
0 (2) 6
(3) 8
0 (4) 12
6. The coordination number of an atom in a tetrahedral hole is four and in an octahedral hole is :
(1) 4
0 (2) 6
(3) 8
(4) 12
crystals is :
000000​

Answer 1

Answer:

1. b
2. c
3. a
4. d
5. b
6. b

Explanation.

1.For NaCl type crystal structure,

          a=2r(Na+)+2r( Cl −)

          a=2×95+2×181

         a=552ppm

2. The ratio of cationic radius to anionic radius in an ionic crystal is greater than 0.732 which corresponds to cubic coordination. So its co-ordination number is 8.

3.In zinc blende structure (ZnS), sulphide ions are face-centred and zinc is present in alternate tetrahedral voids. Coordination number of Zn is 4 and that of sulphide is 4.

4.Number of Na +ions present in the unit cell of NaCl crystal is 4.

5.n NaCl crystal structure, each Na is surrounded by 6 Cl  − ions and each

Cl − is surrounded by 6 Na  +ions.  

6.The hole is said to be a octahedral hole because the hole is surrounded by six atoms