82) Most crystals show good cleavage because their atoms, ions or molecules are:

83) In a solid lattice, the cation has left a lattice site and is located at an interstitial position. The lattice defect is:

84) The ratio of cationic radius to anionic radius in an ionic crystal is greater than 0.732. Its coordination number is:

85) Na and Mg crystallize in bcc and fcc type crystals respectively. The number of atoms of Na and Mg present in the unit cell of their respective crystal is:

86) A solid is made up of 2 elements X and Z. The atoms Z are in ccp arrangement, while the atoms X occupy all the tetrahedral sites. What is the formula of the compound?