The rock-salt (NaCl) structure consists of two mutually interpenetrating face-centred cubic arrays of ions.The rock-salt structure can be viewed based on a ccp array of bulky anions with cations in all the octahedral holes. NiO also have similar type of FCC structure.
Edge length of Unit cell of NiO = 4.18 A
Since in FCC of this type, corner are occupied by anions, an edge consists of a cation and 2 halves of anion :
edge (a) = 2 rNi2+ + 2 rO2- = 2 (rNi2+ + rO2 ) = 4.18 A
or, Bond length = (rNi2+ + rO2 ) = 2.09 A
We assume, that on the face of NiO unit cell, O2- ions contact each other across the diagonal (d) of the face:
So, a2+a2 = d2 or 2a2 = d2
d = 4 rO2- (along the diagonal of Face)
2*(4.18 A)2 = (4 rO2- )2 = 16 rO2- 2
rO2- = 1.48 A
Approximate rNi2+ = 0.61 A
.Nickel oxide crystallizes in the NaCl type of crystal structure. The length of an edge of...
NaCl has a rock salt crystal structure with a unit cell edge length of 0.56 nm. The atomic weights of the Na and Cl are 23 and 35.5 g/mol, respectively, and the Avogadro's number is 6.022 x 10“ formula units/mol. (a) Draw a unit cell to show the crystal structure of the NaCl. (b) What is the coordination number of the atoms in this structure? (c) How many Na atoms and Cl atoms in one unit-cell of such a structure?...
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1. The face-centered gold crystal has an edge length of 407 pm. Based on the unit cell, calculate the density of gold. 2. Gallium crystallizes in a primitive cubic unit cell. The length of an edge of this cube is 362 pm . What is the radius of a gallium atom?
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