Question

(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.

Answer 1

(a) `d = 11.5g//cm^(3)`
edge length (a) `= 300 pm`
atomic mass (M) `= 93 g//mol`
`d = (Zm)/(a^(3) xx Na)`
`11.5 = (Z xx 93)/((300 xx 10^(-10) cm)^(3) xx 6.022 xx 10^(23))`
`Z = (11.5 xx 27 xx 10^(-24) xx 6.022 xx 10^(23))/(93)`
`Z ~ 2.009 ~2`
`:.` It is body -centred cubic unit cell
(b) `{:("Amorphous Solids","Crystalline Solids"),((i) "Constituent particles are not arranged",(i) "Constituents particles are arranged in a regular pattern."),((ii) "Sharp melting point",(ii) "Melt over a range of temperature"),((iii) "Clean cleavage",(iii) "Irregular cut"):}`