00:01
So in this problem, we're given a unit cell for tousinite, which is made of strontium, oxygen, and titanium, which i've reproduced here.
00:10
And we are asked, first, what's the empirical formula of this mineral? so the easiest way to do this is to count.
00:20
So titanium, being in the very center, we just count as one.
00:25
Then for oxygen we have one on each face, so there are six, but only half of it is contained within that cube.
00:34
So we divide that by two, which will give us three.
00:41
And for strontium, we have one on each vertex, so eight, but only a quarter of each strontium, or sorry, only an eighth of a strontium is consistent.
00:58
Contained within one cube because we would consider that if it's on the vertex, then it would also have a cube up over here, up over here, up back here, down here, down here.
01:09
And so we would have, of course, eight different cubes sharing one strong team.
01:15
So an eighth, and if there are eight, so eight over eight, we'll give us one.
01:20
So the empirical formula will be s .r .o .3ti.
01:31
We are then asked how many oxygens are coordinated to titanium.
01:36
So we're just counting adjacent oxygens.
01:39
Now, of course, since titanium is in the center and each oxygen is equal distance away, then each oxygen must be coordinated to the titanium...