which of the following statements is false? a. an atom is the smallest unit of an element that still retains the properties of the element. b. atoms of the various elements differ in their number of subatomic particles. c. all atoms of a particular element have the same number of neutrons in their nuclei. d. protons and electrons are electrically charged particles. e. the neutrons and protons present in the nucleus of an atom are almost identical in mass.