“No familiar conceptions can be woven
around the electron. Something unknown is
doing we don’t know what.”
-Sir Arthur Eddington
The Nature of the Physical World (1934)
“No familiar conceptions can be woven
around the electron. Something unknown is
doing we don’t know what.”
-Sir Arthur Eddington
The Nature of the Physical World (1934)
The ELECTRON:
The Big Bang Theory
The Dilemma of the Atom
•
Electrons outside the nucleus are
attracted to the protons in the nucleus
•
Charged particles moving in curved
paths lose energy
•
What keeps the atom from collapsing?
•
Electrons outside the nucleus are
attracted to the protons in the nucleus
•
Charged particles moving in curved
paths lose energy
Wave-Particle Duality
JJ Thomson won the Nobel prize for describing the
electron as a particle.
His son, George Thomson won the Nobel prize for
describing the wave-like nature of the electron.
The
electron is
a particle!
electron is
The
an energy
The Wave-like Electron
Louis deBroglie
The electron propagates
through space as an energy
wave. To understand the
atom, one must understand
the behavior of
electromagnetic waves.
The electron propagates
through space as an energy
wave. To understand the
atom, one must understand
c =
c = speed of light, a constant (3.00 x 10
8
m/s)
= frequency, in units of hertz (hz, sec
-1
)
= wavelength, in meters
E = h
E
= Energy, in units of Joules (kg·m
2
/s
2
)
h
= Planck’s constant (6.626 x 10
-34
J·s)
Long
Wavelength
=
Low Frequency
=
Low ENERGY
Short
Wavelength
=
High
Frequency
=
High ENERGY
Wavelength TablePractice problems
Wave length (
) (
m
)
Frequency(
)
(
hz
)
NRG (E) (
J
)
Violet
400nm
Blue
475nm
Green
510nm
Yellow
570nm
Orange
590nm
Red
650nm
H-red line 656nm
1. Most show all work to receive full credit.
2. Use the speed of light eqtn (
c =
) to solve for frequency.
Wavelengths must be in m not nm.
Practice problems
Wave length (
) (
m
)
Frequency(
)
(
hz
)
NRG (E) (
J
)
Violet
400nm= 4.00 x 10
-7= 7.5 x 10
14= 5.01 x 10
-19Blue
475nm= 4.75 x 10
-7= 6.32 x 10
14= 4.19 x 10
-19Green
510nm= 5.10 x 10
-7= 5.88 x 10
14= 3.90 x 10
-19Yellow
570nm= 5.70 x 10
-7= 5.26 x 10
14= 3.49 x 10
-19Orange
590nm= 5.90 x 10
-7= 5.08 x 10
14= 3.37 x 10
-19Red
650nm= 6.50 x 10
-7= 4.62 x 10
14= 3.06 x 10
-19H-red line 656nm= 6.56 x 10
-7= 4.57 x 10
14= 3.03 x 10
-191. Most show all work to receive full credit.
2. Use the speed of light eqtn (
c =
) to solve for frequency.
Wavelengths must be in m not nm.
3. Then use that # to solve for NRG (
E = h
)
Answering the Dilemma of the
Atom
•
Treat electrons as waves
•
As the electron moves toward the
nucleus, the wavelength shortens
•
Shorter wavelength = higher energy
•
Higher energy = greater distance from
the nucleus
•
Treat electrons as waves
•
As the electron moves toward the
nucleus, the wavelength shortens
•
Shorter wavelength = higher energy
•
Higher energy = greater distance from
This produces bands
of light with definite
wavelengths.
Electron transitions
involve jumps of
…produces a “bright line” spectrum
Photoelectric Effect
a. Quantum – of nrg is the minimum quantity of nrg
that can be lost or gained by an atom.
b. Photon – is a particle of electromagnetic radiation
having zero mass and carrying a quantum of nrg.
c. Elements can have different levels of nrg.
i. Ground state –little to no nrg
ii. Excited state – higher potential nrg
a. when excited, then return to ground state,
certain gases give off light
Flame Tests
strontium
sodium
lithium
potassium
copper
Bohr’s model:
A. Nucleus is in the center of an atom(like the sun) and the
electrons orbit the nucleus similar to the planets.
B. Used the emission spectrum(photon) to determine nrg
levels
i. Orbits are called shells
a. 1
stshell = 2 electrons
b.2
ndshell = 8 electrons
c. 3
rdshell = 8 electrons etc….
The Bohr Model of the Atom
Neils Bohr
I pictured electrons
orbiting the nucleus much
like planets orbiting the
sun.
I pictured electrons
orbiting the nucleus much
like planets orbiting the
sun.
Quantum Mechanical
Model of the Atom
Mathematical laws can identify the regions
outside of the nucleus where electrons are
most “
likely”
to be found.
Heisenberg Uncertainty Principle
You can find out where the
electron is, but not where it
is going.
OR…
You can find out where the
electron is going, but not
where it is!
“One cannot simultaneously
determine both the position
and momentum of an electron.”
“One cannot simultaneously
determine both the position
and momentum of an electron.”
Electron Energy Level (Shell)
Generally symbolized
by n, it denotes the
probable distance of
the electron from
the nucleus. “n” is
also known as the
Principle Quantum
number
Number of electrons
that can fit in a
Orbital shapes are defined as the surface
that contains 90% of the total electron
probability.
An orbital is a region within an energy level
where there is a probability of finding an
electron.
The
s
orbital has
a spherical shape
centered around
the origin of the
three axes in
space.
There is only 1
type of s orbital.
There are three dumbbell-shaped
p
orbitals in each energy level above n = 1,
each assigned to its own axis (x, y and z)
in space.
Things get a bit more
complicated with the
five
d
orbitals that are
found in the
d
sublevels
beginning with n = 3. To
remember the shapes,
think of “double
dumbells
”
…and a “dumbell
with a donut”!
Energy
Level
(n)
Orbital type
in the
energy level
(types = n)
Number of
orbitals
Number of
Electrons
Number of
electrons per
Energy level
(2n
2)
1
s
1
2
2
2
s
p
1
3
2
6
8
3
s
p
d
1
3
5
2
6
10
18
4
s
p
d
f
1
3
5
7
2
6
10
14
32
A. Distribution of Electrons
i. Atoms are electronically neutral.
ii. There is an electron for every proton in the nucleus.
iii. The larger the atom, the larger the electron cloud.
1. Pauli Exclusion Principle: only two e- can occupy the
same orbital due to the opposite electronic spin .
2. Aufbau Principle: an e- occupies the lowest energy
orbital that can receive it.
3. Hund’s Rule: orbital's of equal energy are each occupied
by one e- before any orbital is occupied by a second e-.
All e- in singly occupied orbital's must have same spin.
1s 2s 2p
Electron Spin
Electron spin
describes the behavior
(direction of spin) of an electron
within a magnetic field.
Possibilities for electron spin:
1
2
1
2
7
s
2
7
p
6
6
s
2
6
p
6
6
d
10
5
s
2
5
p
6
5
d
10
5
f
14
4
s
2
4
p
6
4
d
10
4
f
14
3
s
2
3
p
6
3
d
10
2
s
2
2
p
6
7
s
2
7
p
6
6
s
2
6
p
6
6
d
10
5
s
2
5
p
6
5
d
10
5
f
14
4
s
2
4
p
6
4
d
10
4
f
14
3
s
2
3
p
6
3
d
10
2
s
2
2
p
6
Element
e- Configuration
notation
Orbital notation
Noble gas
notation
Lithium 1s22s1
____ ____ ____ ____ ____ 1s 2s 2p
[He]2s1
Beryllium 1s22s2
____ ____ ____ ____ ____ 1s 2s 2p
[He]2s2
Boron 1s22s22p1
____ ____ ____ ____ ____ 1s 2s 2p
[He]2s22p1
Carbon 1s22s22p2
____ ____ ____ ____ ____ 1s 2s 2p
[He]2s22p2
Nitrogen 1s22s22p3
____ ____ ____ ____ ____
1s 2s 2p
[He]2s22p3
Oxygen 1s22s22p4
____ ____ ____ ____ ____ 1s 2s 2p
[He]2s22p4
Fluorine 1s22s22p5
____ ____ ____ ____ ____ 1s 2s 2p
[He]2s2p5
Neon 1s22s22p6
____ ____ ____ ____ ____ 1s 2s 2p
Practice Problems #2
For Elements # 11-36 answer the following
questions
a. Write the e- ConFig (
arrows
)
b. Write the Orbital Notation (
exponents
)
c. Write the Noble Gas Config (
cheater
)
Due the next Class!!!!!