The element lithium has two stable isotopes, Li-6 and Li-7. How do the atomic structures of these two isotopes compare?
A) Both have 3 protons and 3 electrons, but Li-7 has 4 neutrons.
B) Both have 3 protons and 4 neutrons, but Li-7 has 4 electrons.
C) Li-6 has 3 protons and 3 electrons; Li-7 has 3 protons and 4 electrons.
D) Li-6 has 3 protons, 3 neutrons, 6 electrons, while Li-7 has 3 protons, 3 neutrons, and 7 electrons.