Answer:
Multiply the moles by Avogadro's number ([tex]6.02[/tex] x [tex]10^{23}[/tex]) to get the number of atoms
[tex](0.0255 \ mol)[/tex] * [tex](6.02 \ * \ 10^{23})[/tex]
= 1.5351 x [tex]10^{22}[/tex]
Therefore the answer is 1.5351 x 10^22 atoms in 0.0255 moles of Calcium