question_answer

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

A) The coordination number of each type of ion in \[CsCl\] crystal is 8.

B) A metal that crystallises 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 276 pm.

Correct Answer: B , D

Solution :

[a] The unit cell of \[CsCl\]has bcc arrangement of ions in which each ion has eight oppositely charged ions around it, in the nearest neighbours as shown below :

[b] In bcc, coordination number of metal is 8.

[c] In an unit cell, a comer is shared in eight unit cells and a face centre is shared between two adjacent unit cells.

[d] In \[NaCl\] unit cell; \[2\,({{r}_{N{{a}^{+}}}}+{{r}_{C{{l}^{-}}}})=a\]

\[\Rightarrow \]\[a=2\,(95+181)=552\,pm\]

Thus, incorrect statements in given options [b] and [d].

Solution :

Same as above