The total number of atoms present in 1 mole of   CO₂ are

One mole of substance contains Avogadro’s number (${\mathrm{N}}_{\mathrm{A}}=\hspace{0.17em}6.023\times {\mathrm{10}}^{\mathrm{23}}$ ) of particles. Here, one mole of  CO₂ has 3 moles of atoms or 3N_A  atoms (one mole of carbon atom and 2 moles of oxygen atoms).