What symbol Na plus represents a sodium atom that has lost?

Na is a neutrally charged sodium atom .

Na^(+) is a positively charged sodium cation.

It is given the plus(+) sign because it has lost one electron ' e^(-) '

So the sodium ion contains 11 protons (11+) and 10 electrons (10-)

Summing. 11 + 10 - = 1(+) hence the plus(+) sign.

Latin symbol for sodium, which is 'Nadium'.