C-14 is an isotope of the element carbon. how does it differ from the carbon atom seen here? a) c-14 has two more protons. b) c-14 has two more neutrons. c) c-14 has a larger atomic radius. d) c-14 has two additional valence electrons. this column of the periodic table represents the halogen family. this is a family of reactive elements. how do the members of the family differ? how are they alike? a) the mass numbers differ; they have the same number of protons and valence electrons. b) they have different atomic numbers and mass numbers; they have the same number of electrons. c) they have different atomic numbers and mass numbers; they have the same number of valence electrons. d) they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature. young stars, just beginning their life in the galaxy, would contain mostly a) carbon. b) helium. c) iron and nickel. d) hydrogen and helium.