1. Physics 1202: Lecture 37 Today’s Agenda
Announcements:
Extra credits
Final-like problems
Team in class
Teams 8, 9 & 10
HW 10 due this sFriday
Atomic Physics: finally ! 1

2. Atomic Physics

3. Pauli exclusion principle
Wolfgang Pauli (1925): Nobel 1945
No electron can be in the same quantum state
No more than 2 electrons in an orbital
For a given n, l, m with ms = ± ½
Explains the periodic table
Electronic configuration
Shell structure of atoms

4. Periodic table Atomic structure and chemical properties
Pauli principle: atomic shell model

5. X-ray emission from atoms
X-ray tube
Discovered by Wilheim Röntgen (1895)
Accelerated electrons hit targets
Large potentials kV to MV

6. X-ray emission from atoms
Bremsstrahlung
Continuous x-ray
Electron loosing energy
Minimal l
When all initial K is lost

7. X-ray emission from atoms
K, L, etc. shells and x-ray emission
Fast electron kick inner electron out
Higher electron falls in and fill the “hole”
X-ray emitted

8. X-ray emission from atoms
Each element has a specific spectra
lmin

9. Nuclear Physics

10. The nucleus Ernest Rutherford (1909-1910)
Discovered the nucleus (Nobel 1908 Chem.)
Using alpha particles on gold film
Large deflection: tiny but massive positive nucleus

11. The neutron Why mass & charge do not “fit”
mHe ~ 4 mH but only qHe = 2 qH (ion)
Rutherford in 1920 speculated
Neutral particle with about mass of proton must exist
James Chadwick (Nobel 1935)
Discovered the neutron (1932)
Neutral particles (mass about 0.14% larger than p)
Not photon (pass through matter), but massive:kick proton

12. The nucleus Made of Size and shape A Z protons N neutrons
Mass number A = Z + N A Z
Size and shape
Almost spherical
Not always though
1.2 X m
=1.2 fm

13. The strong nuclear force
A force must exist to compensate electric repulsion
Nuclear force
Always attractive
The same between
protons or neutrons
100 times stronger
than electrostatic
force
Short-range:
about only 3 fm

14. The strong nuclear force
Neutron are essential
Provide the “glue” to maintain protons together
Meed more n as A grows

15. Binding energy “missing” mass = negative or binding energy
The mass of an atom is less than its constituents
12C (m=12 u): used to defined the atomic mass unit u
6 protons + 6 neutrons + 6 electrons
Adding = u
“missing” mass = negative or binding energy
E = mc2