Answer:
8.42 moles (3 sig. figs.)
Step-by-step explanation:
Given 5.07 x 10²⁴ atoms of antimony (Sb) => ? moles Sb
1 mole of any substance contains 6.02 x 10²³ particles ( atoms or molecules)
∴ Think in terms of 'how many 6.02 x 10²³'s are in 5.07 x 10²⁴ atoms Sb?
That is => moles Sb = 5.07 x 10²⁴ atoms Sb / 6.02 x 10²³ atoms Sb/mole Sb
= 8.42192691 moles Sb (calculator answer) ≅ 8.42 moles (3 sig. figs.)