# Quantum model of an Atom Chapter 17 - PowerPoint PPT Presentation

1 / 33

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.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Quantum model of an Atom Chapter 17

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

#### Presentation Transcript

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

• An up and down path that the particle travels in as it moves.

• A back and forth path that the particle travels in as it moves.

• Not a traditional wave at all but instead is a function that tells us the probability of detecting the particle.

Newton’s Laws ok

### Perspective

largesmall

fast

slow

Relativity

Wave-Particle Duality

250

0

10

### Standing waves are created when

• Waves reflect and bounce back to where they started from.

• Waves wrap around and come back to where they started from.

• Both 1 and 2 are ways standing waves can be created.

### 2 Dimensions

• It is easy to create standing waves in 2 dimensions as well.

Two waves on a drum head

A single wave 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.

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 d2Y(x)

8 p2m dx2

+ V(x) Y(x) = EY(x)

### Three Dimensional Atomic Orbitals

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

s

p

### Orbital Patterns

• Three waves: Electrons will resonate in “s”, “p” and “d” orbitals.

One orbital

s

p

d

### 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.

e

-

e

-

### 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.

Spin Down Spin Up

High energy

Low energy

1

2

3

### 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).

### Electrons in an Atom: Energy WellsFill the lowest energy orbitals first

free electron

Zero Energy

3d

3p

3s

Level 3

2p

Level 2

2s

Energy

It is negative for a bound electron

Level 1

1s

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

250

0

• 1

• 2

• 3

• 6

250

0

10

• 3

• 5

• 9

• 16

250

0

10

• 4

• 6

• 10

• 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

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s

### Emission line spectra revisited

• It can then fall down creating the emission spectrum for that element.

free electron

3d

3p

3s

Level 3

2p

Level 2

2s

Level 1

1s