Atomic Nuclear 1

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=10-15m). A nucleus is 1015 times denser than water!

Investigation of the structure of the atomic nuclei is still a frontier.

Atomic Nuclear 2

The 12C NucleusThis picture depicts the 12C 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.

Atomic Nuclear 3

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 + 1H

Atomic Nuclear 4

Properties of Neutrons – cont.Magnetic Dipole Moments

Ex(kev) T1/2 Spin m(nm)

0 10.6 m 1/2+ -1.9130427(5)

Atomic Nuclear 5

Notice

I think I’ve merged these slides into Atoms.ppt earlier