Assertion : An important feature of Fluorite structures is that cations being large in size occupy FCC
lattice points whereas anions occupy all the tetrahedral voids giving the formula unit (A: cation B: anion).
Reason : There are 6 cations and 12 anions per FCC unit cell of the Fluorite structure.
Assertion : In NaCl crystal each Na ion is touching 6 ions but these ions do not touch each other.
Reason : The radius ratio roe is greater than 0.414, required for exact fitting.
Assertion : The ratio of and F- per unit cell of ZnS and is 1:2.
Reason : In ZnS ions occupy alternate tetrahedral voids and in F- ions occupy all the tetrahedral voids of FCC unit cell.
Sodium metal crystallizes in bcc lattice with cell edge . The radius of sodium atom will be-
(D) None of these
The edge length of cube is 400pm. Its body diagonal would be-
(A) 500 pm
(B) 693 pm
(C) 600 pm
A metallic element exists as cubic lattice. Each edge of the unit cell is 2.88 . The density of the metal is 7.20 g . How many unit cell will be present in 100 g of the metal -
Iron crystallizes in a b.c.c. system with a lattice parameter of 2.861 . Calculate the density of iron in the b.c.c. system (Atomic weight of Fe = 56, )
An alloy of copper, silver and gold is found to have copper constituting the ccp lattice. If silver atoms occupy the edge centres and gold is present at body centre, the alloy has a formula-
Frenkel defect is not found in the halides of alkali metals because alkali metals have
1. high electropositivity
2. high ionic radii
3. high reactivity
4. ability to occupy interstitial sites