Transcript Lec 2

Announcements
To join clicker to class today:
– Turn on the Clicker (the red
LED comes on).
– Push “Join” button followed
by “20” followed by the
“Send” button (switches to
flashing green LED if
successful).
•Pick up paper copy of
periodic table if you do not
have text here or a table
you can write on.
Review
– History of atomic models:
• e- embedded in positive sphere (~1900)
• Rutherford Experiment (1910) lead to idea of dense positively
charged nucleus with e- somewhere outside
Review
• e- don’t fall into nucleus because trapped in
“quantized” energy levels.
– Evidence = quantization of light energy (photons,
photoelectric effect) plus emission and absorption line
spectra.
– Can calculate energy of emission or absorption from ∆E = EfEi
• Simple equation for energies of light from H atoms.
– Rydberg equation: 1/  = R(1/nf2 - 1/ni2),
• where R = a constant,  = observed wavelength, nf =
integer (quantum number) representing the final energy
level, ni = integer(quantum number) representing the
initial energy level. n=1,2,3....
• Do not need to know since just a special example of ∆E
= Ef-Ei
Review
• First simple model Bohr model En = -Rhc/n2,
– Rhc = 2.179 x 10-18 J/atom
– note E < 0
 with E = 0
– Problem orbiting e- should fall into nucleus.
– highest E-level is n=
Quantum # Rules
•Pauli Exclusion Principle: No two e- in the same atom
may have all four quantum numbers the same.
•n (principle) = 1, 2, 3 ...∞ (specifies shell)
•l (angular momentum QN) = 0, 1, ...n -1 (0=s,1=p, 2=d,
3=f)
•ml(magnetic QN) = 0, ±1, ... ±l.
•ms=±1/2