The reaction Ba(NO3)2(aq) + Na2SO4(aq) >> 2NaNO3(aq) + BaSO4(s) goes to completion because a
1. gas is formed
2. precipitate is formed
3. unionized product is formed
4. soluble salt is formed

2. precipitate is formed

Explanation:

In this reaction barium nitrate and sodium sulfate solutions react to form a barium sulfate precipitate.Barium and sulfate ions will react to give barium sulfate precipitate where as the sodium and nitrate ions are spectator ions.

The net ionic equation after removing unchanged ions from each side of the full ionic equation will be;

Ba²⁺+ SO₄²⁻ →  BaSO₄ (s)

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."