Transcript Aim: How can we explain models of the atom?

Aim: How can we explain
energy transitions in an atom?
Do Now:
What were the limitations of the Rutherford model of
the atom and how did the Bohr model explain these
limitations?
Emission Spectra
• When electron falls from
higher to lower level, photon is
emitted.
• Shows as bright series of
lines.
Visible spectrum
Balmer Series
• Named after
Johann Jacob
Balmer
1825-1898
Gas Tube
Demo
Energy of photon
emitted or absorbed
Energy of
initial level
Energy of
final level
Calculate the energy of the photon
emitted when a hydrogen atom
changes from energy state n = 3 to
n= 2, in eV and Joules
Ephoton = Ei – Ef
Ephoton = -1.51 eV – (-3.40 eV)
Ephoton = 1.89 eV
1.89 eV * 1.60 x 10-19 J = 3.0x10-19 J
1 eV
For a mercury electron
transition from level c to a,
calculate Ephoton, λ, f, and the
type of EM wave emitted.
Ephoton = Ei – Ef
Ephoton = -5.52 eV – (-10.38 eV)
Ephoton = 4.86 eV
4.86 eV * 1.60 x 10-19 J = 7.77 x 10-19 J
1 eV
Ephoton = hc
λ
7.77 x 10-19 J = (6.63x10-34 J•s)(3 x 108 m/s)
λ
λ = 2.56 x 10-7 m
c= fλ
3.00 x 108 m/s = f (2.56 x 10-7 m)
f = 1.17 x 1015 Hz
This is ultraviolet light
An electron in a hydrogen atom
drops from n = 4, n = 2. Find
Ephoton (eV and Joules), f, and the
color of light.
Ephoton = Ei – Ef
Ephoton = -0.85 eV – (-3.40 eV)
Ephoton = 2.55 eV
2.55 eV * 1.60 x 10-19 J = 4.08 x 10-19 J
1 eV
Ephoton = hf
4.08 x 10-19 J = (6.63 x 10-34 J•s)f
f = 6.15 x 1014 Hz
This is blue light
Calculate the energy of the
photon needed when a hydrogen
atom changes from n =1 to n =∞
Ephoton = Ei – Ef
Ephoton = -13.60 eV – 0.00 eV
Ephoton = -13.60 eV
Ionization Potential
• Minimum energy needed to
remove an electron from the
ground state to infinity
• For hydrogen  -13.6 eV
• For mercury  -10.38 eV
• A positive photon energy
indicated photon is
emitted
• A negative photon
energy indicates photon
is absorbed
Absorption Spectra
• When electron jumps to a
higher energy level a
photon is absorbed.
• Shows up as a series of
dark lines.
Wave Model
• After De Broglie proposed matter waves,
he was able to show the Bohr model could
be explained by considering the orbits of a
series of waves
Cloud Model (Shrödinger’s
Model)
• Quantum mechanics indicates
the probability of the electron
being in a certain area
• Most probable regions are in
area called ‘electron cloud’
• Energy levels of Bohr model
are divided into sublevels and
orbitals -- together with Cloud
model define the current
model
Erwin Shrödinger
1887-1961