By X-ray studies, the packing of atoms in a crystal of gold is found to be in layers such that starting from any layer, every fourth layer is found to be exactly identical . The density of gold is found to be 19.4 g cm^(-3) and its atomic mass is 197 a.m.u. The length of the edge of the unit cell will be

By X-ray studies, the packing of atoms in a crystal of gold is found t

1.	By X-ray studies, the packing of atoms in a crystal of gold is found to be in layers such that starting from any layer, every fourth layer is found to be exactly identical . The density of gold is found to be 19.4 g cm^(-3) and its atomic mass is 197 a.m.u. The length of the edge of the unit cell will be
Answer» 407 pm 189 pm 814 pm 204 pm Solution :`RHO=(ZxxM)/(a^3xxN_0xx10^(-30))` or `a^3=(ZxxM)/(rhoxxN_0xx10^(-30))` For ccp, i.e., f.c.c., Z=4. HENCE,`a^3=(4xx197)/(19.4xx6.02xx10^23xx10^(-30))` `=6.747xx10^7` =`67.47xx10^6` or `a=(67.47)^(1//3)xx10^2` `=4.07xx10^2` pm =407 pm