What Went Wrong in My NaCl Density Calculation?

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SUMMARY

The discussion focuses on the calculation of the density of sodium chloride (NaCl) using atomic weights and ionic radii. The user calculated the volume of Na and Cl as 4.2 ų and 24.4 ų, respectively, leading to a total volume of NaCl as 28.6E-23 cm³. The calculated mass of NaCl was determined to be 9.7E-23 g, resulting in a density of 3.39 g/cm³, which significantly deviates from the accepted density of 2.17 g/cm³. The discrepancy is attributed to the need for calculating the volume of the unit cell to account for the space between ions.

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Iyafrady
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I want to find the ensity of NaCl given the atomic weight of Na is 23 and that of Cl is 35.5.The ionic radius are 1A and 1.8A respectively.I foundthevolume of each element to be Vna=4.2A^3 and Vcl=24.4A^3.

V(NaCl)=28.6E-23
MASS(NaCl)=[(23+35.5)g/mole]*(1/avogadros number)=9.7E-23
So D=m/v=(9.7E^-23)/(28.6E-23)=3.39

but this is way off from the listed density of 2.17g/cm^3...dont know what I am doing wrong.
 
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There is a lot of space between those spheres, you know...

You have to calculate volume of the unit cell.
 

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