An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. The atomic number represents the number of protons in the atom, so boron has 5 protons. The atomic mass (mass number) is the sum of protons and neutrons, so with a mass number of 11 and 5 protons, boron has 6 neutrons (11 - 5 = 6)