1 mol of any substance (atoms, molecules...)=6.022*10²³ particles (atoms, molecules....)
we calculate the number of representative particles in 0.00856 mol of NaCl.
1 mol---------------------------------6.022*10²³ particles.
0.00856 moles-------------------- x
x=(0.00856 mol * 6.022*10²³ particles) / 1 mol≈5.1548*10²¹ particles.
we have 1.1548*10²¹ particles in 0.00856 mol NaCl.