Asked by Dr Bob plz help

The crystal structure of lithium sulfide (Li2S) is pictured here. (Intro 1 figure) The edge length of the unit cell is 5.88*10^2^2 pm.

i guess it is FCC ( face cenred cubic)

1--

What are the coordination numbers of and Li^+ and S^2- in the lithium sulfide crystal shown? Enter the values in order of Li^+ and S^2-, respectively.

Ans... i though it shld be 4,4 .. but it says " Face ions are shared between two unit cells."...

plz someone

2- How many formula units are in the unit cell shown for Li2S ?

Ans- i gues it shld be 1 but it says -
The formula represents one formula unit. How many sets of are in the unit cell?
Answered by DrBob222
I don't have the book and can't see the picture. I can't find anything on the Internet so I'm passing on this one. I've also looked in all the references I have at home and can't find anything on Li2S.
Answered by Mrs C
The Number of Formula Units is 4, but I don't know why, I just happened to guess it and it marked it as correct for me.
As for part 1, I don't know :(
Answered by Dash
It's 4,8. Easy, you just count the lines, but note that the S(2-) is on the surface, so it's surrounded by the Li+ of the adjacent unit cell as well as its own.
Answered by Anonymous
What is the density of Li2S in grams per cubic centimeter? this was the 3rd part of this question :/
Answered by friend
The density of lithium sulfide is 1.5g/cm^3
Answered by SJ
the number of formula units is 4: there are 4 Sulfur atoms in the unit cell (8* 1/8 + 6* 1/2) and 8 Lithium atoms (all contained within the unit cell)
Answered by Anonymous
1) 4,8

2) 4
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