Such an attachement may form by attraction of the positively one atom for the negatively of another atom, or by the attraction of charged atoms, which are

Protons, electrons, ions.

Explanation: An atom is made up of three basic particles which are protons, electrons and neutrons. Protons have positive charges, electrons have negative charges while neutrons have no charge i.e.,neutrons are neutral. Protons and neutrons occupy the nucleus while electrons revolve around the nucleus in their orbits. The number of protons is equal to the number of electrons in a neutral atom, but when an atom loses an electron it becomes positively charged while when it gains an electron, it becomes negatively charged. These charged atoms are called ions.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.