A solid AB crystallises as NaCl structure and the radius of the cation is 0.100 nm. The maximum radius of the anion can be:

0.137 nm
0.241 nm
0.274 nm
0.482 nm

Solution

In a solid ‘AB’ having the NaCl structure, ‘A’ atoms occupy the corners of the cubic unit cell. If all the face-centered atoms along one of the axes are removed, then the resultant stoichiometry of the solid is

AB₂
A₂B
A₄B₃
A₃B₄

Solution

How many unit cells are present in a cube-shaped ideal crystal of NaCl of mass 1.00 g ?[Atomic masses : Na = 23, Cl =35.5]

5.14× 10²¹ unit cells
1.28 × 10²¹ unit cells
1.71× 10²¹ unit cells
2.57 × 10²¹ unit cells

Solution

Schottky defect generally appears in :

NaCl
KCl
CsCl
all of these

Solution

Schottky defect occurs in ionic crystals of type A+ B–, when equal number of cations and anions are missing from their lattice sites so that the electrical neutrality is maintained. This defect generally appears in highly ionic compounds which have high coordination number.NaCl, KCl and CsCl all have high coordination numbers i.e., 6, 6 and 8 respectively. So, Schottky defect appear in all of the given compounds.

CsBr has bcc structure with edge length 4.3. The shortest interionic distance in between Cs⁺ and Br^– is

3.72
1.86
7.44
4.3

Solution

Hexagonal close packed arrangement of ions is described as

ABC ABA
ABC ABC
ABABA
ABBAB

Solution

ABAB...... is hexagonal close packing.

When molten zinc is converted into solid state, it acquires hcp structure. The number of nearest neighbours of Zn will be

Solution

hcp is a closed packed arrangement in which the unit cell is hexagonal and coordination number is 12.

Equal number of atoms or ion missing from normal lattice point creating a vacancy due to

Frenkel defect
Mass defect
Schottky defect
Interstitial defect

Solution

The vacancy created due to missing of equal no. of atoms or ions form normal lattice point is called Schottky defect. In this type of defect electrical neutrality of ionic crystal is maintained.

In the solid state, MgO has the same structure as that of sodium chloride. The number of oxygens surrounding each magnesium in MgO is

Solution

Since MgO has a rock salt structure. In this structure each cation is surrounded by six anions and vice versa.

Na and Mg crystallize in bcc and fcc type crystals respectively, then the number of atoms of Na and Mg present in the unit cell of their respective crystal is

4 and 2
9 and 14
14 and 9
2 and 4

Solution

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