The dots in the Lewis dot structure symbolize an atom's elements.
Since Na^+ is a positive ion (cation) with a charge of +1, it indicates that it has lost an electron.
Since Na had one electron, to begin with, and it is now lost, Na^+ will have no dots. However, the charge must still be written as a superscript.
Therefore, the Lewis dot structure for Na^+ is just Na^[+]
