2.1 x 10⁵⁶ atoms
The mole is the number of particles(molecules,atoms,ions) contained in a substance
1 mol = 6.02.10²³
number of atoms :
[tex]\tt 3.49\times 10^{32}\times 6.02\times 10^{23}=2.1\times 10^{56}[/tex]