Chemistry
posted by Odesa .
Chemical analysis of a silicon crystal reveals gallium at a level of 3.091X10^2 atomic percent. Assuming that the concentration of thermally excited charge carriers from the Si matrix is negligible, what is the density of free charge carriers (free carriers/cm3) in this Si crystal?

1.598e14.

an explanation please?
i need a formula! 
The answer is not right, at least for me. anyone who knows how to do it and could write how ?

Please, I need the formula!

The answer 1.598e14 was not right for me too. Any ideas what happen and how to write it out?

What is the formula to use

Please, I need the formula!

The data for everyone of us is different as you noticed formula is required

Go to back to H4P2

As its Si: 5.00*10^22 / (gallium level*10^2) by someguy

1.5455*10^19

gallium level*10^2) what is this?

What is the formula, please?

What about 3.091*10^7? please

H4P2

1.6265*10^14 i have the answer for 3.091*10^7
here the caculation
atomic percent*NA(avogadro number)
the solution/atomic volume of gallium 
1.5442*10^14
this is the corect ones 
step1
(6.023*10^23)/(12.05)=m
step 2
m*(level of atomic percent)*(10^2)