Gamma rays have the highest penetrating power so it can only be stopped by thick layers of dense metal. :)
Atomic mass Ca = 40 a.m.u
1 mole Ca ----------- 40 g
2.5 mols Ca -------- ( mass Ca )
Mass Ca = 2.5 x 40 / 1
Mass Ca = 100 / 1
= 100 g of Ca
hope this helps!
you have to show us the rest of it because we have no idea what your looking at. I'm sorry
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