For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
The cations and anions being oppositely charged attract each other through strong coloumbic forces and form an ionic bond.
(1) Sodium is carrying +1 charge called as cation and chloride is an anion carrying -1 charge. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral .
(2) Sodium is carrying +1 charge called as cation and phosphate is an anion carrying -3 charge. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral .
(3) Sodium is carrying +1 charge called as cation and sulfate is an anion carrying -2 charge. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral .
(4) Sodium is carrying +1 charge called as cation and carbonate is an anion carrying -2 charge. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral .
(5) Potassium is carrying +1 charge called as cation and chloride is an anion carrying -1 charge. They form .
(6) Potassium is carrying +1 charge called as cation and phosphate is an anion carrying -3 charge. They form .
(7) Potassium is carrying +1 charge called as cation and sulfate is an anion carrying -2 charge. They form .
(8) Potassium is carrying +1 charge called as cation and carbonate is an anion carrying -2 charge. They form .
(9) Calcium is carrying +2 charge called as cation and chloride is an anion carrying -1 charge. They form .
(10) Calcium is carrying +2 charge called as cation and phosphate is an anion carrying -3 charge. They form .
(11) Calcium is carrying +2 charge called as cation and sulfate is an anion carrying -2 charge. They form .
(12) Calcium is carrying +2 charge called as cation and carbonate is an anion carrying -2 charge. They form .
(13) Ammonium ion is carrying +1 charge called as cation and chloride is an anion carrying -1 charge. They form .
(14) Ammonium ion is carrying +1 charge called as cation and phosphate is an anion carrying -3 charge. They form .
(15) Ammonium ion is carrying +1 charge called as cation and sulfate is an anion carrying -2 charge. They form .
(16) Ammonium ion is carrying +1 charge called as cation and carbonate is an anion carrying -2 charge. They form .
(17) Iron is carrying +3 charge called as cation and chloride is an anion carrying -1 charge. They form .
(18) Iron is carrying +3 charge called as cation and phosphate is an anion carrying -3 charge. They form .
(19) Iron is carrying +3 charge called as cation and sulfate is an anion carrying -2 charge. They form .
(20) Iron is carrying +3 charge called as cation and carbonate is an anion carrying -2 charge. They form .
According to the law of definite proportion "every chemical compound contains fixed and constant proportions (by mass) of its constituent elements." (Encyclopedia Britannica)
We can see in the question that the ratio of flourine to sulphur in compound A is 1.18 while the ratio of flourine to sulphur in compound B is 2.37.
The two chemical compounds do not contain a fixed proportion by mass of their constituent elements therefore, they can not be same compound according to the law of definite proportions.