The CORRECT statement(s) for cubic close packed (ccp) three- dimension

1.	The CORRECT statement(s) for cubic close packed (ccp) three- dimensional structure is (are)
Answer» The number of neighbours of an atom PRESENT in the topmost layer is 12. The EFFICIENCY of the atom packing is 74 % The number of octahedraland tetrahedral voids per atom are 1 and 2 respectively. The unit cell edge length is `2sqrt2` times the radius of the atom. SOLUTION :(a) is incorrct because for any atom in the top most layer, coordination number is not 12 as there is no layer above the topmost layer . (b) is a known FACT. is correct because in ccp (fcc), number of atoms per unit cell is 4. HENCE, octahedral voids =4 and tetrahedral voids =8. therefore , number of octahdral voids per atom =1 and number of tetrahdral voids per atom =2 (d)For ccp (fcc), ` r= a/(2sqrt2) or a = 2sqrt2 r `

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