(a) An element has atomic mass `93 g mol^(_1)` and density `11.5 g cm^(-3)`. If the edge length of its unit cell is 300 pm, identify the type of unit cell.
(b) Write any two differences between amorphous solids and crystalline solids.

Explanation

Given, Atomic weight (M)=93 g `mol^(-1)`
Density= 11.5 g `cm^(-3)`
Edge length (a) = 300 pm = `3xx 10^(-8)` cm
We know that -
Density, `d=(("Z M"))/(N_(A) xx a^(3))`
Substituting the values -
`11.5 g cm^(-3) = ((93 "g mol"^(-1) xx Z))/(6.023 xx 10^(23) xx (3xx10^(-8) cm)^(3))`
Or, `Z=([11.5 g cm^(-3) xx 6.023 xx10^(23) xx (3xx10^(-8) cm)^(3)])/(93g mol^(-1))`
`Z = 2.01~~2`
Hence, the number of atoms present in one unit cell is 2 which indicates a body centered cubic system.