Transcript Structure and Properties of the Nucleus

Phosphorescent materials continue to glow
after the lights are turned off. How can you
use the model of an atom to explain this?
Structure and Properties of the
Nucleus
Nucleons
Proton is the nucleus of the simplest atom,
hydrogen. It has positive charge (+e) and mass
mp=1.6726x10-27 kg.
Neutron is electrically neutral and has mass
mn=1.6749x10-27 kg
Nuclei that contain the same number of
protons but different number of neutrons
are called isotopes.
Nuclear Radii
r  (1.2  10
15
1/ 3
m) A
Atomic Mass Unit
1u  1.6605 10
27
kg  931.5MeV / c
2
Binding Energy and Nuclear
Forces
The total mass of a stable nucleus is
always less than the sum of the masses
of its constituent protons and neutrons.
The total energy represents the amount of
energy that must be put into a nucleus in
order to break it apart into its constituent
protons and neutrons.
To be stable, the mass of nucleus must be
less than that of constituent nucleons, so
that energy input is needed to break it
apart.
Radioactivity
Radioactivity is the result of the
disintegration or decay of instable
element.
Alpha Decay
Smoke Detectors
Transmutation
parent
daughter
Q-Value
The energy released is called the
disintegration energy, Q or Q-value:
Q  (M P  M D  M )c
2
Beta Decay
Gamma Decay
1. Which of the three types of radiation will interact with
electric field?
2. Why do beta rays and alpha rays deflect in opposite
directions when moving through a magnetic field?
Baby-Quiz
1. Where would you most likely find an electron in the
first excited state for a one-dimensional box?
2. Why do some minerals glow when they are illuminated
with ultraviolet light?
3. The wavelength of red light is 600 nm. An electron
with a speed of 1.2 km/s has the same wavelength. Will
the electron look red? Explain.
4. An electron and proton have the same speeds. Which
has the longer wavelength? Why?