Answer:
7 moles
Explanation:
The molecular formula of sodium sulfide is Na_2S
One molecule of Sodium sulfide has 2 atoms of sodium and one atom of sulfur
1 mole of Sodium sulfide has 2 moles of sodium and one mole of sulfur
so 3.5 moles of sodium sulfide will have 2× 3.5 moles of sodium atoms
i.e 2×3.5= 7 moles of sodium atom
