Dear Student,
The compound formed between potassium(K+) and carbonate(CO3-2) is Potassium Carbonate (K2CO3)
The compound formed between sodium(Na+) and sulphide(S-2) ions is Sodium Sulphide (Na2S)
The Compound formed between ammonium (NH4+) and phosphate (PO4-3) is ammonium phosphate (NH4)3PO4
Regards!