We are talking about Na2CO3. This compound is called sodium carbonate. It is also sometimes referred to as soda ash. It dissolves in water in two different stages. The first dissociation stage produces the bicarbonate ion.
Na2CO3 --> Na+ + NaCO3-
The second dissociation stage is the bicarbonate ion turning into the carbonate ion.
NaCO3- --> Na+ + (CO3)2-
The net overall dissociation equation for sodium carbonate is the summation of both stages. It is shown below.
Na2CO3 --> 2Na+ + (CO3)2-
So we can see that each sodium carbonate molecule dissociates in water to give 2 sodium cations and one carbonate anion.