Answer:
There are 9.635 x 10^23 atoms in 1.6 moles of selenium
Explanation:
To solve this problem you have to use Avogadro´s constant (6.022 x 10^23).
In 1 mol of any element there are 6.022 x 10^23 atoms, so in 1.6 moles there will be...
1 mol Se ------------- 6.022 x 10^23 atoms
1.6 moles Se ------ x = 9.635 x 10^23 atoms.