How many moles of sodium atoms are contained in 3.5 moles of sodium sulfide

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