Question

An atom of sodium has an atomic mass of 23 and an atomic number of 11. The atom contains
23 protons, 23 electrons, and 11 neutrons.
11 protons, 11 electrons, and 12 neutrons.
11 protons, 12 electrons, and 11 neutrons.
23 protons, 12 electrons, and 23 neutrons.

Answer 1

the second choice, the atomic number plus the number of neutrons equals the atomic mass.