[填空题]
Common salt, NaCl, has a densit0dt m.x; y,*oud tgx-1ys xi(imn-zp 5y qzpdtw+6l3*rof $ 2.165\ \text{g/cm}^3 $. The molecular weight of NaCl is 58.44. Estimate the distance between nearest neighbor Na and Cl ions. [Hint: Each ion can be considered to have one "cube" or "cell" of side $ s $ (our unknown) extending out from it.] $s$ = nm
