Answer:
Having difficulties !!! screen shotted it :)
16. H20 - Covalent
17. Mn(NO2)2 - Ionic and called Manganese(II) nitrate
18. HgO - Ionic
19. Li3N - Covalent
In order to get HgO you would need 2Hg+1O2=2HgO. Since oxygen is diatomic you need two when it stands alone causing you to need two mercuries to balance out the reactants and the product I hope this helps
The answer is the first one, Xe