Crystals can be classified into how many basic crystal systems?

$CdS$ crystallizes in which type of crystal system?

Find the Weiss indices for the plane $(231)$.

Which of the following crystal systems has $a = b = c$ and $\alpha = \beta = \gamma \neq 90^o$?

$A$ solid compound $XY$ has $NaCl$ structure. If the radius of the cation is $100 \ pm,$ the radius of the anion $(Y^-)$ will be .............. $pm$.

The triclinic unit cell has the following parameters: