First you need to work out what mass of 84g of stainless steel is nickel, and because there's 5% you can simply divide by 20, giving 4.2g
For this you can use the equation
![Moles= \frac{Mass}{Mr}](https://tex.z-dn.net/?f=Moles%3D%20%5Cfrac%7BMass%7D%7BMr%7D%20)
The mass, as was worked out previously, is 4.2g
The Mr, which is found on the periodic table, is 28
Moles =
![\frac{4.2}{28}](https://tex.z-dn.net/?f=%20%5Cfrac%7B4.2%7D%7B28%7D%20)
= 0.15mol
1mol = 6.023 x
![10^{23}](https://tex.z-dn.net/?f=%2010%5E%7B23%7D%20)
atoms
So, 0.15mol = 0.15 x 6.023 x
![10^{23}](https://tex.z-dn.net/?f=%2010%5E%7B23%7D%20)
= 9.0345 x
![10^{22}](https://tex.z-dn.net/?f=10%5E%7B22%7D%20)
atoms