Answer:
The answer to your question is
1.- 1.686 x 10²⁴ atoms
2.- 0.25 moles
Step-by-step explanation:
1.- 
 1 mol ---------------- 6.023 x 10²³ atoms
 2.8 moles ---------- x
 x = (2.8 x 6.023 x 10²³) / 1
 x = 1.686 x 10²⁴ atoms
2.- 1 mol ------------------ 6.023 x 10 ²³ molecules
 x moles ------------- 1.50 x 10²³ molecules
 x = (1.50 x 10²³ x 1) / 6.023 x 10²³
 x = 0.25 moles