Lithium forms $BCC$ structure having an edge length of unit cell $351 \ pm$. What is the atomic radius of lithium (in $pm$)?

$Assertion (A)$: White tin is an example of a tetragonal system. $Reasoning (R)$: For a tetragonal system,$a=b=c$ and $\alpha=\beta=\gamma \neq 90^{\circ}$. The correct answer is

Which type of unit cell from the following is common to all seven types of crystal systems?

Which of the following has a structure similar to a matchbox?

The space lattice of graphite is

The triclinic unit cell has the following parameters: