If there are #2.50xx10^18# lead atoms, what is the mass of this quantity?
I don't know the mass of a ream of lead, and I have never heard of lead being measured with this quantity.
But the number of atoms of any elemental quantity is
And thus if there were
I'm not quite sure how much lead you have but this is how to calculate the number of atoms:
As an example, if you have
This is a lot of lead!