Electrons in Atoms
5.2 Electron Arrangement in Atoms
5.3 Physics and Quantum Mechanical
Model
The Nora School
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Chemistry
Period _______
Filling Electron Orbitals
• At this point, we know that
electrons fill spaces known
as orbitals.
• Electron configurations,
or the way they fill these
orbitals follow three very
specific rules:
– Aufbau Principle
– Pauli Exculsion Principle
– Hund’s Rule.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Chemistry
Period _______
Aufbau Principle
• The Aufbau Principle
simply states that each
electron occupies the
lowest energy level first.
• The diagram at right is
know as an Aufbau
diagram.
• How many electrons can
each line occupy?
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Chemistry
Period _______
1
Pauli Exclusion Principle
• This principle states that only two
electrons may occupy the same
sublevel.
• Those two electrons must also have
opposite spins indicated by adjacent
opposite arrows.
The Nora School
Chemistry
955 Sligo Avenue
Silver Spring, Maryland 20910
Period _______
Hund’s Rule
• Lastly, electrons spread out to occupy
orbitals of the same energy before
doubling up.
The Nora School
Chemistry
955 Sligo Avenue
Silver Spring, Maryland 20910
Period _______
Some Practice
• For each, complete the
orbital filling diagram
then indicate the short
hand version:
–
–
–
–
–
–
Orbital Filling Diagram
Na (12)
Fe (26)
Se (34)
Ar (18)
I (53)
Ag (47)
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Chemistry
Period _______
2
The Periodic Table and Electron
Configuration
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Chemistry
Period _______
Theory of Light
• Early conception of light
was that it was made up of
particles.
• By 1900, there was enough
experimental evidence to
demonstrate that light was
made up of waves.
• Waves consist of many
characteristic movements
that can be used to
describe its movement.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Chemistry
Period _______
Light as a Wave
• Light can be depicted as having an up and
down motion of a continuous wave.
• Wave Vocabulary:
– Crest: Wave highpoints
– Trough: Wave lowpoints
– Amplitude: High of the wave from the midpoint.
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Chemistry
Period _______
3
Properties of Waves
F=c/λ
(c= speed of light)
• The distance between two
consecutive crests or
troughs is known as a
wavelength (λ).
• The number of oscillations
a wave makes in a given
number of time is known
as frequency (f).
Measured in Hertz.
• Knowing this, how is
wavelength and frequency
related?
The Nora School
Chemistry
955 Sligo Avenue
Silver Spring, Maryland 20910
Period _______
The EM Spectrum
• Visible light (colored light ranging from red
to violet) is only a very small part of the large
group of radiation waves known as the
Electromagnetic Spectrum.
Which wave has the
highest frequency?
Which wave has the
largest wavelength?
The Nora School
955 Sligo Avenue
Silver Spring, Maryland 20910
Chemistry
Period _______
4