4.00 moles of sodium has a mass of 91.96 grams.
To find an element's molar mass, you can use its atomic weight.
Its a covalent bond for this q
Li2S + 2 HNO3 --> 2 LiNO3 + H2S
Li2 S + H2 N2 O2 --> Li2 N2 O5 + H2 S
Li S + H2 N2 O5 -> Li N2 O5 + H2 S
Li2 S2 + H4 N4 O10 --> Li2 N4 O10 + H4 S2
Li^2 S^2 + H^4 N^4 O^10 --> Li^2 N^4 O^10 + H^4 S^2
Ionic compounds generally occur between metals and non-metals due to their large electronegativity difference. You can simple go down Group 1 and Group 17 of the periodic table.
Examples:
NaCl (Sodium Chloride)
KCl (Potassium Chloride)
RbCl (Rubidium Chloride)
CsCl (Cesium Chloride)