Which of the following statements are true? I. The number of protons in an element is always the same for all neutral atoms of that element. II. The number of electrons in an element is always the same for all neutral atoms and ions of that element. III. The number of neutrons in any element is always equal to the number of protons of that element. IV. The number of neutrons in an element can sometimes vary – resulting in the formation of an unstable isotope that is slightly more (or less) massive than the stable atom of the same element. Group of answer choices I, II, and IV are true I, II, and III are true II and III are true I and II are true I and IV are true