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Transcript
Review of Atomic Orbitals
1923 –
Electron has the properties of a particle and a w a v e
(constructive/destructive interference)
1926 –
Quantum Mechanics
• Schrödinger solves a “wave equation” for the total energy of 1
electron and 1 proton.
• A series of “wave functions” results. These correspond to the
various states of an electron.
From wave functions (ψ), we get
1) The energy associated with an electronic state
2) The relative probability of finding an electron in a location in
space (ψ 2)
E
3p (3)
3s
2p (3)
2s
1s
f and d levels are not very
important in organic chemistry
Shapes of Atomic Orbitals
a “wave”
+
+
+
–
–
Signs are not related to electric charge or probability
–/–, +/+ interfere constructively, +/– interfere destructively
1s-orbital
2s-orbital
nucleus
node
(–)
(+)
•
(+)
•
y
(+)
–
–
+
z
(–)
2py-orbital
x
2px-orbital
+
2pz-orbital
1s, no nodes; 2s & p, 1 node; 3 s & p, 2 nodes, etc.…
“Orbitals” are regions in space where the probability of finding an
electron is high (ψ 2 = 95%). Orbitals are not “real”!
Filling Atomic Orbitals
3p
3s
2p
degenerate orbitals equal in energy
2s
1s
Orbitals are filled in this order with the following rules.
1)
Aufbau principle
place electrons in lowest level, work up max 2/per orbital
2)
3)
Pauli exclusion principle. Electrons have two possible spin states.
To be in an orbital together, they must be paired (opposite)
or
or
paired
unpaired
Hundʼs Rule
Add one electron to each orbital with spins unpaired, when each has one,
double up and pair.
Why? Electrons repel each other!
C
N
O
F
4
3
2
1
Ne
full
Shapes of Molecules by VSEPR
Methane
Ammonia
Boron Trifluoride
Theory