Question

Pressure on $NaCl$ crystal in inc. what in effect on coordination no?

Answer 1

$Nacl$ Crystal structure have 6:6 coordination number. On applying pressure , ion come closer to each other which result in more compact structure or close pack . thus increase in pressure changes the coordination number of $NaCl$ crystal from 6:6 to 8:8 which is $CsCl$ type crystal structure.