Atoms may have different numbers of neutrons. Atoms are the smallest fraction of an element that can exist, and still show the properties of the element. They consists of electrons (negatively charged), protons (positively charged), and neutrons (no charge). The number of electrons is equivalent to the number of protons normally however an atom may loose or pick up electrons and have a positive charge or negative charge. The number of neutrons in the nucleus may vary within a given element to give varieties of atoms we call isotopes.
They can enter your blood stream (via breathing/ingesting) and once in your bloodstream they can enter cells and mutate your dna, which can cause cancer/birth defects/ reproductive harm
I would think of a unicellular organism or a plant, but I'm not too sure on this one, Just trying to help :)
