There's growing evidence ...Fentanyl (or hydromorphone) have a better side effect profile than morphine (remember the vaunted vasodilation is only a side effect) thereby making fentanyl a better choice..
The subatomic particles in the nucleus of a carbon atom are protons and neutrons. The atomic nucleus contains protons and usually neutrons (except for hydrogen-1 (protium) atoms. The number of protons is an element's atomic number and is the same for all atoms of an element. Carbon has atomic number #6#. So all atoms of carbon have #6# protons in their atomic nuclei.
But these basic atomic components are by no means the only known subatomic particles. Protons and neutrons, for instance, are themselves made up of elementary particles called quarks, and the electron is only one member of a class of elementary particles that also includes the muon and the neutrino.