face-centered cubic lattice

[LetsSmile]

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when NaCl crystallizes in a face-centered cubic lattice of chloride ions with the the smaller sodium ions occupying holes btwn the chloride ion, how many Cl- ions are in contact with any single Na+ ion?

Since it's in a face-centered cubic lattice, I did:

(6 x 1/2) + 1 = 4

But the answer is 6.

Do you have any idea?

 

[grayzkule]

Think of it like a pair of dice. One die is a cube and has six sides. The Na+ is the die and the Cl- are the sides.

 

[kkhan]

..dont understand this question either?? Is there a formula that works for all scenarios?

 

[Shinpe]

I don't know of any formula, but I just pictured a Cube-centered lattice basic unit in my head. If you do that and then put the sodium ion in the middle of it, you'll see that you have 6 chlorides surronding it. 4 to the sides and 2 above and below it. Hope that helps.