Finding the percent void of the crystalline structure of NaCl [closed]








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> 
> Find the percent of void in the crystal structure of $\ce{NaCl}$.
> 
> 
> 


I am trying to calculate the percent void of the packing structure of $\ce{NaCl}$. Let's denote radius of anion as $r$, radius of cation as $R$. What I know


$$\text{side length} = 2R + 2r$$


$$R + r = \pu{2.50 Å}$$


The ratio of cation radius to the anion radius is $0.600$. The equation to find void space:


$$100 \times \frac{\text{total volume} - \text{volume of spheres}}{\text{total volume}}$$


Yes, this is a homework question, but I'm stuck and I just need some help to get started.


