Reaction of metal carbonate with acids It is said that acids react with metal carbonate to form salt carbon dioxide and water.

Sodium carbonate reacts with hydrochloric acid to form sodium chloride , carbon dioxide and water
But if we ionise them then sodium carbonate dissociates to form  two sodium ions and carbonate ion and hydrochloric acid disassociates to form two hydrogen ion and two chlorine Ion so the sodium Ion will combine with the chloride Ion to form NaCl and the hydrogen ions will combine with carbonate ion and form carbonic acid but this doesn't happen and they form carbon dioxide and water.
WHY?
Hydrochloric acid is already dissociated to $\ce{H+}$ and $\ce{Cl-}$

Sodium carbonate as ionic compound dissolves as

$$\ce{Na2CO3(s) &lt;=&gt; 2 Na+(aq) + CO3^2-(aq)}$$

Chloride and sodium ions are in this reaction called the spectator/bystander ions, not being involved in the reaction.

The ongoing reactions are these :

$$\ce{ 2 H+ + CO3^2- &lt;=&gt;&gt; H2CO3 &lt;=&gt;&gt; H2O + CO2(aq)}$$

followed by the dissolution equilibrium:

$$\ce{ CO2(aq) &lt;=&gt; CO2(g)}$$

If solution is lead to crystallization, the spectator ions then meet to form ionic crystals, keeping their charges.

$$\ce{Na+(aq) +  Cl-(aq) &lt;=&gt; NaCl(s)}$$