The atomic number of carbon is six, which means that a carbon atom has six protons. Carbon has three naturally occurring isotopes: carbon-12, carbon-13, and carbon-14. A. All carbon atoms have six neutrons.
B. All carbon atoms have six protons and six electrons.
C. Atoms of all carbon isotopes have either more than 6 electrons or fewer than 6 electrons.
D. Atoms of some naturally occurring carbon isotopes may have six neutrons.
E. Atoms of some naturally occurring carbon isotopes may have twelve neutrons.