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
The mass, as was worked out previously, is 4.2g
The Mr, which is found on the periodic table, is 28
Moles =
= 0.15mol
1mol = 6.023 x
atoms
So, 0.15mol = 0.15 x 6.023 x = 9.0345 x 
atoms
For this you can use the equation
The mass, as was worked out previously, is 4.2g
The Mr, which is found on the periodic table, is 28
Moles =
1mol = 6.023 x
So, 0.15mol = 0.15 x 6.023 x