Answer: Option (a) is the correct answer.
Explanation:
Atomic number of sodium is 11 and its electronic distribution is 2, 8, 1. Whereas atomic number of sulfur is 16 and its electronic distribution is 2, 8, 6.
So, when both sodium and sulfur chemically combine together then it results in the formation of an ionic bond due to transfer of an electron from sodium to sulfur atom.
Sodium changes into [tex]Na^{+}[/tex] by losing an electron and sulfur changes into [tex]S^{2-}[/tex] by gain of two electrons from two sodium atoms.
As it is known that water is a polar solvent and all ionic substances will dissolve in water.
Therefore, we can conclude that when the compound, [tex]Na_2S[/tex], is mixed with water, the [tex]Na_2S[/tex] is soluble because all [tex]Na^{+1}[/tex] compounds are soluble in water.
