How many protons, neutrons, and electrons are in a neutral Na-23 atom?

Sodium has atomic number 11, so it has 11 protons.
A neutral atom has the same number of electrons as protons, so it has 11 electrons.
Neutrons = mass number - protons = 23 - 11 = 12.
The atom has 11 protons, 12 neutrons, and 11 electrons.