Which of the following statement(s) is/are correct ?

Options

A. The coordination number of each type of ion in CsCl crystal is 8
B. A metal that crystallizes in bcc structure has a coordination number of 12
C. A unit cell of an ionic crystal shares some of its ions with other unit cells
D. The length of the unit cell in NaCl is 552 pm.
`(r_(Na)=95 pm, r_(Cl^(-))=181 pm)`

Answer

A, C, D

Explanation

The crystal to CsCl has bcc(body centred cubic) structure. In such an arrangement the coordination number of both is 8. in case of NaCl, two interpenetrating fcc crsytal lattices are present, out other of `Cl^(-)` ions only. Each `Na^(+)` ion is located half-way between two `Cl^(-)` ions and each `Cl^(-)` ion is located half way between two `Na^(+)` ions. in a unit cell of NaCl, `Cl^(-)` occupy corners as also the face centres and `Na^(+)` ions are located at octaheral voids. On each of a unit cell we have two `Cl^(-)` ions and one `N^(+)` ion. Hence,
`a=2(r_(Na^(+))+r_(Cl^(-)))=2(95+181)`pm=552pm
Hence (A,C,D) are correct options.