Question

In Na+ what does + sign indicates?

Answer 1

It means that it is a positive sodium ion, with 11 protons and 10 electrons.

Sodium's atomic number is 11, which means that it has 11 protons, and would be a neutral atom with 11 electrons. However, sodium is extremely unstable with 11 electrons, because this would leave its 3s electron shell only half full. So, it will lose an electron (in very dramatic fashion), leaving one more positive charge than negative, hence the + symbol.