Transcript Notes: electron configurations orbital diagrams

Notes: electron configurations
orbital diagrams
A new approach to the atom,
Quantum Mechanical Model (Erwin Schroedinger)
• Atomic Orbital:
Is the region around a
nucleus where an
electron is likely to
be found.
• Probability of finding
an electron at a
particular location is
shown as a blurry
cloud of negative
charge.
• Dense cloud = higher
probability
Atomic Orbitals
• 4 categories of orbitals, each has a
unique shape and electron
capacity.
Orbital type is designated by the letters:
s
p
d
f
Spherical
Perpendicular
Diagonal
Forget it!
The ‘s’ orbitals. Region where electron
is likely to be found
• Increasing quantum number, designates increasing energy,
and therefore a “larger” orbital. An increased energy
electron, will spend more of its time farther from the
nucleus.
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Orbital Energy
Electrons fill from low
energy to higher energy.
– 1 at a time
– Maximum of 2 per
orbital
– s=1 orbital
– p=3 orbitals
– d=5 orbitals
– f=7 orbitals
5s
4p
3d
4s
3p
3s
2p
2s
1s
Electron Configurations
Where are all the electrons supposed to be in a ground
state (un-excited) atom?
3 Guidelines:
1. aufbau Principle
2. Hund’s Rule
3. Pauli Exclusion Principle
3 guidelines to place electrons
aufbau
• aufbau Principle:
– Electrons are added one at a time to the lowest
energy orbitals available until all electrons have
been accounted for.
3 guidelines to place electrons:
Pauli Exclusion Principle
• An orbital can hold a maximum of 2
electrons
• Electrons in the same orbital spin in
opposite directions.
– 2 e- in an orbital = paired electrons
– 1 e- in an orbital = unpaired electron
3 guidelines to place electrons:
Hund’s Rule
• Electrons occupy equal energy orbitals to
maximize the unpaired electrons.
• For example in the n=2 p -orbitals
(there are 3p orbitals)
there will be 1 electron in each,
before there are 2 electrons in any.
ORBITAL Capacity
“s” 1 orbital
“p” 3 orbitals px, py, pz
“d” 5 orbitals
“f” 7 orbitals
Orbital Energy
Electrons fill from low
energy to higher energy.
– 1 at a time
– Maximum of 2 per
orbital
– s=1 orbital
– p=3 orbitals
– d=5 orbitals
– f=7 orbitals
5s
4p
3d
4s
3p
3s
2p
2s
1s
Relative Energy of Orbitals
• Use the arrow method
to determine.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f,…
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1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
7p
3d
4d 4f
5d 5f
6d 6f