Certain naturally occurring radioactive isotopes are unstable: Their nucleus breaks apart, undergoing nuclear decay. ... All elements with 84 or more protons are unstable; they eventually undergo decay. Other isotopes with fewer protons in their nucleus are also radioactive.
D. Making the reactant particles larger
The atom's center, or nucleus, is positively charged and the electrons that whirl around this nucleus are negatively charged, so they attract each other. The reason the force is strong is because the atom is so small. The distance between the nucleus and the electrons is about 1 Angstrom (named after a famous scientist); this is 0.00000001 cm (10-8 cm) or about 4 billionths of an
