Which of the following statements are true?
1. 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.