How are ions formed?
The flaw in the question is exactly what Gaurang Tandon said: $\ce{H3O^+}$ is formed by a water molecule and a proton ($\ce{H^+}$), not a hydrogen atom.

Compare the number of electrons in both sides of the following two equations:

$$\ce{H2O + H^+ -&gt; H3O^+}$$

$$\ce{H2O + H^. -&gt; H3O^+}$$

The last equation is wrong: there's an extra electron in the left hand side.