Question

how many protons are in one atom of sodium-23?

Answer 1

sodium is number 11 in the periodic table, so it contains 11 protons.
(the periodic table is ordered in number of protons in one atom of the material, so with a look on the table you can easily find any proton number of any element :) )

Answer 2

The number of protons in an atom is different for every element. If you look at the periodic table, then the number labeled "atomic number" is the number of protons.