Download Chapter 5: Electrons in Atoms

Chapter 5: Electrons in Atoms
Table of Contents
• Chapter 5: Electrons in Atoms
– 5.1: Light and Quantized Energy
– 5.2: Quantum Theory and the Atom
– 5.3: Electron Configuration
REVIEW: History of the Atom
Dalton
Thomson
All matter is
made of tiny,
indivisible
atoms
(demo)
Plum pudding
model
Rutherford
Positive nucleus
and electrons in
empty space
around the
nucleus
REVIEW: History of the Atom
• Bohr’s model and eventually the Electron
Cloud model were developed in part to
explain the different colors of light when
elements burn
5.1
Light & Energy
Wave Nature of Light
• Light behaves like a wave
–Wavelength (λ ) - distance between crests
on wave (m)
–Frequency (ʋ) – number of waves per
second (Hz or 1/s or s-1)
Light & Energy
5.1
Wave Nature of Light
• Electromagnetic Radiation - energy with wavelike behavior.
2 parts: electric field and magnetic field
Light & Energy
5.1
Wave Nature of Light
• All electromagnetic waves travel at the speed of light (c):
3.00 x 108 m/s
c = λν
• c = speed of light (m/s)
• λ = wavelength (m)
• ν = frequency (/s or Hz)
Light & Energy
5.1
Wave Nature of Light
PRACTICE:
c = λν
• c = speed of light = 3.00 x 108 m/s
• λ = wavelength = ???
• ν = frequency = 5.10 x 1014 /s
c
÷
λ×ν
λ = c/ν = 3.00 x 108 m/s ÷ 5.10 x 1014 /s
= 5.88 x 10-7 m
Light & Energy
5.1
Wave Nature of Light
PRACTICE:
c = λν
• c = speed of light = 3.00 x 108 m/s
• λ = wavelength = 2.50 x 10-6 m
• ν = frequency = ??
c
÷
λ ×ν
• ν = c/ λ = 3.00 x 108 m/s ÷ 2.50 x 10-6 m
= 1.20 x 1014 /s
5.1
Light & Energy
Electromagnetic Spectrum
• Electromagnetic spectrum – the range of wavelengths of
electromagnetic radiation
• LIGHT: all wavelengths on the spectrum
5.1
Light & Energy
Electromagnetic Spectrum
• Electromagnetic spectrum – the range of wavelengths of
electromagnetic radiation
• LIGHT: all wavelengths on the spectrum
5.1
Light & Energy
Sketch the EM Spectrum (use p. 120 in text)
Light & Energy
5.1
Visible Light
low
energy
high
energy
Red
Orange
Yellow
Green
Blue
Indigo
Violet
White light is the combination of all the
visible colors of light
Light & Energy
5.1
Check
• What are the two fields in electromagnetic
radiation?
electric field and magnetic field
• Which EM radiation has the highest energy?
– Gamma rays
• Which has the lowest energy?
– Radio waves
• What are the colors of visible light?
– ROYGBIV
5.1
Light & Energy
Particle Nature of Light
• Wave model doesn’t explain light’s interaction
with matter.
• Einstein proposed that light also behaves like
a particle
5.1
Light & Energy
Particle Nature of Light
• When high frequency light hits metal, a
photon is released.
• Photon – particle of light energy
5.1
Light & Energy
Emission Of Light
• Quantum – minimum amount of
energy that can be gained or lost by
an atom; a packet of energy
• Photon –carries a quantum of
energy.
5.1
Light & Energy
Electrons & Light
• Bohr’s Model of the Atom:
Electrons orbit the nucleus in
fixed orbits around the nucleus.
• Light (EM radiation): Caused when excited electrons
“jump” from one energy level (orbital) and then return to
original energy level (orbital)
Light & Energy
5.1
Electrons & Light
• As energy is absorbed,
electrons move from their
ground state (original
energy level) to an excited
state (higher energy level)
Initial position
)
)
nucleus
)
ground state
1
2
energy levels
)
3
)
4
Final position
)
5
)
excited state
6
7
Light & Energy
5.1
Electrons & Light
• Electrons are unstable in
their excited state, so they
return to the ground state by
releasing energy. During this
return, light is emitted!
Final position
)
)
nucleus
)
ground state
1
2
energy levels
)
3
)
4
Initial position
)
5
)
excited state
6
7
5.1
Light & Energy
Emission Of Light
To calculate the energy in a photon:
E = h· ν
• Where
– E = energy in Joules (J)
– h = Planck’s constant 6.626 x 10-34 J·s
– ν = frequency (Hz or /s)
Light & Energy
5.1
Particle Nature of Light
PRACTICE:
E = h· ν
h = Planck’s constant = 6.626
x
10-34
• E = energy = ???
• ν = frequency = 5.10 x 1014 /s
E
J·s
h
÷
×ν
E = h x ν = 6.626 x 10-34 J·s x 5.10 x 1014 /s
= 3.38 x 10-19 J
Light & Energy
5.1
Particle Nature of Light
PRACTICE:
E = h· ν
h = Planck’s constant = 6.626
x
10-34
• E = energy = ???
• ν = frequency = 7.23 x 1014 /s
E
J·s
h
÷
×ν
E = h x ν = 6.626 x 10-34 J·s x 7.23 x 1014 /s
= 4.79 x 10-19 J