quantum model of an atom chapter 17
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Quantum model of an Atom Chapter 17. 0 of 250. 10. I read Chapter 15 before coming to class. Yes, the whole thing. Nope, essentially none. Well some, more than ½. A little only. 250. 0. The wave nature of moving particles is interpreted as being. - PowerPoint PPT PresentationTRANSCRIPT
Quantum model of an Atom Chapter 17
I read Chapter 15 before coming to class
Yes, the whole thing. Nope, essentially ... Well some, more t...
A little only.
0% 0%0%0%
1. Yes, the whole thing.
2. Nope, essentially none.
3. Well some, more than ½.
4. A little only.0of
250
10
The wave nature of moving particles is interpreted as being
An up and down pa.. A back and forth pa.. Not a traditional w...
4%
90%
6%
1. An up and down path that the particle travels in as it moves.
2. A back and forth path that the particle travels in as it moves.
3. Not a traditional wave at all but instead is a function that tells us the probability of detecting the particle.
0
250
Perspective
large small
fast
slow
Newton’s Laws ok
Relativity
Wave-Particle Duality
Standing waves are created when
Waves reflect and... Waves wrap aroun... Both 1 and 2 are ...
38%
62%
0%
1. Waves reflect and bounce back to where they started from.
2. Waves wrap around and come back to where they started from.
3. Both 1 and 2 are ways standing waves can be created.
100
250
Standing Waves
2 Dimensions
It is easy to create standing waves in 2 dimensions as well.
A single wave on a drum head
Two waves on a drum head
Three waves on a drum head
Wrap standing waves around a point
These are patterns of vibration.
Bohr Model Explained!
Take de Broglie’s waves and wrap them in a standing wave pattern around the nucleus.
Put one wave , then two waves, then three waves, etc and you exactly predict the location of the Bohr radii!
A CRUDE representation!
The Quantum Model of the Atom
Electrons are found in 3-D electron probability waves.
They do not orbit. Instead they exist in the locations given by standing wave clouds.
We call these wave clouds orbitals to reflect the fact that the electrons do not orbit like a planet.
Three Dimensional Atomic Orbitals The shape and energies of the actual
orbitals depend on the number of standing waves in the pattern. They are found from solving the Shrödinger Wave equation:
h2 d2(x) 8 2m dx2
+ V(x) (x) = E(x)
Kinetic Energy + Potential Energy = Total Energy
Orbital Patterns
One wave:Electrons will resonate in one
pattern, called an “s” orbital.
Two waves:Electrons will resonate in
two patterns, “s” and “p” orbitals
s p
s
Orbital Patterns
Three waves: Electrons will resonate in “s”, “p” and “d” orbitals.
s
p d
One orbital
S Orbitals
All numbers of standing waves have “s” orbitals.
They are all round but their interiors are different.
Still, in each case there is just one orbital.
P Orbital
P orbitals come in sets of 3, whether there are 2 waves or 3 waves or more.
D Orbitals
D orbitals come in sets of 5, whether there are 3 waves or 4 waves or more.
Orbital Patterns
The pattern continues on as s, p, d, f, g, h, i, j, etc. Each new orbital set has two more orbitals than the previous one.
Orbital Type s p d f g h i j
Orbitals in set 1 3 5 7 9 11 13 15
Standing Waves 1 2 3 4
Orbital Types s s,p s,p,d s,p,d,f
Total Orbitals 1 4 9 16
The Pauli Exclusion Principle
At most two electrons can occupy the same orbital. If two electrons are in the same orbital, they must have different spins.
e-e-
Spin Down Spin Up
Orbital Type s p d f g h i j
Orbitals in set 1 3 5 7 9 11 13 15
Electrons 2 6 10 14 18 22 26 30
Understanding Atoms How do electrons fill the orbitals as
we move along the periodic table? Electrons fill the lowest energy levels
first. For the lighter atoms, fewer standing waves and simpler orbitals usually means lower energies.
From here on I’ll refer to number of standing waves (physics lingo) as energy levels or shells (chemistry lingo).
High energy
123
Low energy
Electrons in an Atom: Energy WellsFill the lowest energy orbitals first
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
Energy
It is negative for a bound electron
Zero Energy
Hydrogen
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
Helium
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
Lithium
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
Beryllium
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
Boron
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
Carbon
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
Nitrogen
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
Oxygen
free electron
1s
2s2p
Level 1
Level 2
Level 33d3p3s
What is the maximum number of electrons in the entire set of p orbitals of any given shell?
1 2 3 6
25% 25%25%25%
1. 12. 23. 34. 6
0
250
How many orbitals all together are in the third shell by itself?
3 5 9 16
25% 25%25%25%
1. 32. 53. 94. 16
100
250
How many electrons total are in an atom that has the first and second shells completely filled?
4 6 10 12
25% 25%25%25%
0
250
10
1. 42. 63. 104. 12
Absorption line spectra revisited The outer electron of any atom can
jump up to higher orbitals creating a unique absorption spectrum for that element
free electron
1s
2s2p
Level 1
Level 2
Level 3 3d3p3s
Emission line spectra revisited
It can then fall down creating the emission spectrum for that element.
free electron
1s
2s2p
Level 1
Level 2
Level 3 3d3p3s