1. Atomic Nuclear1 Atomic Nuclei Radius of an atom ~ 10 –10 m (Å, Angstrom unit) Radius of a nucleus ~ 10 –15 m (fm, fermi or Femto-meter) Atomic nuclei are composite particles made up of protons and neutrons. These two particles are collectively known as nucleons. Each nucleon is about 2000 times more massive than an electron, and they are packed together in a space only several fermis wide (1 fermi=10 -15 m). A nucleus is 10 15 times denser than water! Investigation of the structure of the atomic nuclei is still a frontier.

2. Atomic Nuclear2 The 12 C Nucleus This picture depicts the 12 C nucleus, 6 proton and 6 neutron, but no one know how they are arranged or if they exist as individual nucleons. Properties of protons have been given. The neutron mass is given in the Data Sheet. Although neutral, it has a spin of ½ and a magnetic moment. As mentioned earlier, in terms of fundamental particles, nucleons are made up of u and d quarks.

3. Atomic Nuclear3 Properties of Neutrons Mass: 1.0086649 +- 0.0000000 amu Mass Excess: 8071.323 +- 0.002 keV Binding Energy: 0.000 +- 0.000 keV Beta Decay Energy: 782.353 +- 0.002 keV Spin: ½+ Half life: 10.4 min Mode of decay: n   + 1 H

4. Atomic Nuclear4 Properties of Neutrons – cont. Magnetic Dipole Moments Ex (kev) T 1/2 Spin m(nm) 010.6 m 1/2+ -1.9130427(5)

5. Atomic Nuclear5 Notice I think I’ve merged these slides into Atoms.ppt earlier