I've been studying a bit of chemistry over the past month and this question just so happened to be one that it looked like I might be able to understand, so I figured I would try solving it using the methods I've learned so far. Here goes:

1.) 518g of Spodumene (LiAlSi

_{2}O

_{6})

Breaks down to:

- 310.8g of O (518g / 10 = 51.8g - - considering 6 parts oxygen, we have 51.8*6 = 310.8g)
- 103.6g of Si (number obtained in a manner analogous to the above example)
- 51.8g of Li (as above)
- 51.8g of Al (as above)

2.)Using an atomic weight of 6.94 for Li, we then have 7.46 moles of Li (51.8g / 6.94)

3.)To obtain the number of atoms present in the 7.46 moles of Li we take 7.46 * 6.02x10

^{23} which comes out to 4.49x10

^{24} which is the number of atoms of Li present in our 518g sample of Spodumene.

4.)Considering the question specifically asked for the number of

**Li-6** atoms, I believe (per Borek's informative post) that we would take 7.3% of this above number. So, 4.49x10

^{24} * .073 =

**3.2777x10**^{23}, which should be the number of Li-6 atoms in the sample?

I'm reasonably certain I did okay up until step 4. I don't really understand how to isolate the number of a certain isotope of an element as is requested in the problem, but using Borek's post I took a whack at it.