Here’s what people said they learned.

1

Difference between molecular formula and empirical formula.

Welding is a physical transformation. (Mostly)

It’s not terrible to not use a calculator.

Ionic compounds: datingMolecules: married

How to user periodic table better.

LSU is the best school to go to

EVER!

The vertical columns on the periodic tables FEATURE elements with similar properties & behaviors.

I need to read those CEF guides!

Water is a bent molecule, ain’t no HO.

All is not lost!

Here’s what people said they wanted to know better.

3

Ionic compound formulas.

How to classify what is solid, liquid or gas?

Balancing equations…where to begin.

Why is H2O2 so much stronger as an oxidant than H2O?

Problems on the quiz.

When will we start naming ions?

Calculator or no-calculator? I went no-calc and made a 65. I never made a 65 before.

How to get an A on the midterms.

Molecular formula vs. empirical formula.

http://bezmuke.blogspot.com/2009/07/tigri-lei-gheparzi-leoparzi-pisici.html

Rarely, people forget to tear off their “action item for self study”; here is one such example.

4

I want to revisit our energy relations

5

W = E = mad (energy due to acceleration) = mv2/2 (kinetic energy)E = W = mgh (potential energy against gravity)Q = m C TAnd E = mc2

There are more! How about E = h

Does anyone recognize E= t iV ?

Where are we?

6

We have measured mass of proton: 1.66 x 10-24 gWe have measured mass of electron: 1836 times lighter than protonWe have measured charge of proton: +1.602 x 10-19 CoulombsWe have measured charge of electron: -1.602 x 10-19 CoulombsWe know protons are at the center of atom.Neutrons were found—fixed the problem of “missing” atomic masses.We expect neutrons to be at the center of atom, too (why?).We imagine electrons are distributed around the atom somehow,

like satellites in orbit.Because the electrons are so fast, we imagine them doing most of

work of chemistry: the currency of chemistry is electrons!

I want to look at percents: here’s a CEF question.

The nucleus contains approximately what percent of an atom’s mass ?

•  10.02%• 60.49%• 80.50%• 99.97%

7

 It’s going to depend on the atom, but ignore that and answer the question: ATQ.

4We are still in:

Read Chapters #4 later.

8

Now we need to learn something about waves.

9

Well, there are 2 kinds:

Longitudinal (sound)

Transverse (light)

Let’s make some longitudinal waves with a speaker.

10

High and low frequencies travel at the same speed (almost).

The sound gets louder and softer as we travel about the room.

This speed is called c = 1140 feet/second (in air).

How long does it take sound to travel 1 mile?

Drums & cymbals are the original woofers and tweeters.

(Maybe boomers and clangers would be better).

11http://www.replayphotos.com/lsuphotos/traditions-pictures/band_T_OBN__0001024.cfm

Low frequency = long High frequency = short

Speed = frequency wavelength

12

c = “nu” “lambda”

Let’s get those units!

Pinpointing the electron positionsrequired 2 breakthroughs, one conjecture, and a lot of theoretical work.

hc

E

13

The Einstein/Planck breakthrough (early 1900s).

1) Light can have wave AND particle properties!2) The particles are called photons.3) Each photon carries energy of:

h = Planck’s constantc = speed of light = 3 x 108 m/s

Low energy = long wavelength = redHigh energy = short wavelength = blue

Graceful swans vs. hummingbirds

14

Hey, what what are the units of energy again?

15

Energy is the capacity to do work.It has work units.Work is force times distance.Force is mass times acceleration.So…. E W = f d = m a d

Units: kg (m/s2) m = kgm2/s2

This thing is called a Joule

Joule, Calorie, Speed of light are all things worth remembering.

1 Joule = 1 ntm = kg m2/s2

4.184 Joule = 1 Calories = 0.001 Food Calories

Planck’s constant: 6.63 x 10-34 Js c = 3 108 m/s (= 186,000 miles

per second)

16

How far IS 186,000 miles?

Here’s a real-world sample problem.

17

A device we use to measure the size and shape of molecules at CAMD (out on Jefferson Highway) produces 3 x 107 photons per second at l = 1.5 Ǻ (0.15 nm). What is this power output in Joules?

Remember Emission Spectra—what was the

point anyway?

18

Bohr atom (the hypothesis): electrons have to stay on specific paths.

19

Dotted orbit: the “ground” state of hydrogen.Solid orbit: one of the excited states of hydrogen in a discharge tube.

When an electron in the excited state drops to lower

state, light is emitted.

20

When an electron comes out of a high orbit, into a lower one, light is given off. From the wavelength, , you can calculate the difference in energies between the orbits.

21

E = hc /

We always deal with CHANGES in energy; absolute energy is a mystery.

Needless to say, there are Bohr-ring videos!Energy transitions: http://www.youtube.com/watch?v=8TJ2GlWSPxI&feature=results_video&playnext=1&list=PLC1E620BA406E7A75

Bohr-Ring Children: http://www.youtube.com/watch?v=PLpZfJ4rGts

Bohr-Ring Voice: http://www.youtube.com/watch?v=Ic8OnvRonb0

What is this, physics?

Where is the chemistry?

22

View periodic tables!

23

# of electrons = 2n 2

n = 1, 2, 3….2n

2 = 2, 8, 18…Energy and the number of electrons an orbit canhold both increase with n.

To explain* the periodic table, Bohr proposed that the number of electrons each orbit can support grows with the energy of that orbit, described by an “energy quantum number”, n :

*It can be argued that Bohr did not yet explain the table, but he figured out its “code”.

24

Periodic Table in its Standard Form

n=1 so 2n2 = 2 2 elements on top rown=2 so 2n2 = 8 8 elements on 2nd rown=3 so 2n2 = 18 ooops!

Hey, it works….for small atoms.

1st row of periodic table: 2 atoms

2nd row: 8 atoms3rd row: ooops!

25

That is a big “ooops” and, besides, Bohr was not able to explain WHY the electrons had to circle around on these discrete, quantized orbits.

The periodic table we usually see cuts out Actinides and Lanthanides, “problem” elements with l=3 (f orbitals). This wide-screen version is better.

26

http://www.sciencegeek.net/tables/LongTable2000.png

The de Broglie Breakthrough (1924): Electrons are waves

(and particles).

27

Wave-particle duality= h/mv   or... mv= h

(h = 6.63 10-34 Js)

v = velocity

m = mass

Oh great….now even chemists, the masters of electrons, need to understand waves. Let’s do

waves again.

28

Oldest physics joke: what’s ?

pronounced “nu”

pronounced “lambda”

Waves diffract. They can “stand” if the dimension of their

“container” is right.

29

Wave addition is weird: out-of-phase waves cancel.

30

+ =Nothing

In phase waves add.

31

+ =Bigger wave.

Waves bounce (with inversion).

32

What if there’s another wall located 4 wavelengths away?The waves “stand”. See later videos of standing waves.

33Now is a good time to Wiki.

What if there’s another wall located 4.25 wavelengths away?

34

It’s much better with video!

35

http://www.youtube.com/watch?v=-gr7KmTOrx0

http://www.youtube.com/watch?v=-gr7KmTOrx0

String standing waves

There is no net dissipation of energy in “standing waves”.

36

Hmmm…..atoms don’t seem to need to have energy added, either, but where’s their wall?

Do we need a wall for a standing wave?

After crossing between the walls twice, the essentialfeature is that the wave has come back to whereit once was.

Bohr’s circular orbits turn out to be wrong, but we can at least see why orbits must be quantized: the waves would cancel themselves out unless the ends meet smoothly. This is called a “boundary condition”.

37

Circumference = 2i where i = 1, 2, 3

Node

Crest

Trough

There are no walls and no circular orbits in a real atom, but electrons are nevertheless “confined” in a zone, like sand on a vibrating plane:

38

http://www.youtube.com/watch?v=GtiSCBXbHAg

Click for standing waves without walls

Note the complexity of the wave goes up with frequency…and one wave pattern gives way to another by a “jump”.

When you work the math…

39

the actual position of electrons can't really be specified best we can do is say where they PROBABLY are

they tend to locate in cloud-like zones (called orbitals, not orbits)

Orbital shape gets more complex with electron energy.

These shapes sort of "fall out of" the mathematics;no human would have predicted them intuitively.

Additional quantum numbers describe these shapes.

Erwin Schrödinger

Orbital shapes can be strange. Note the extra quantum

numbers! http://www.albany.net/~cprimus/orb/

40

n=1, l=0, m=0

n=2, l=0, m=0

n=2, l=1, m=0

n=3, l=1, m=0

n=3, l=2, m=0

n=4, l=3, m=1

s-type p-type d-type (top)f-type (bottom)

Quantum Numbers are not that hard!

41

Our purpose: Introduce the four quantum numbers Explain how they relate to chemical periodicity Explain how they relate to orbital shape & size

Give some more examples of physical periodicities These are really the keys--keys as in open the door to molecular understanding.

So pay attention!

 

42

Four numbers describe more than 100 elements…that’s a beautiful simplification.

This will help you understand angular momentum.This will help you understand angular momentum.

But why do we have to learn Quantum Numbers? Isn’t that arcane?

43

Because I had to learn Russian.And square dancing.

Try reading Zen & the Art of Motorcycle Maintenance! It’s about the quality of life, which definitely includes knowledge.

It is easier to fit in when you know stuff.

Quantum makes it easier to understand later material.

And Lissajous patterns.And tennis.

You will be buying quantum computers.

Quantum Numbers are beautiful!

And accounting.

http://www.youtube.com/watch?v=Ee_uujKuJMI

A useless journey….but beautiful.

44

Mt. Chapin TrailRocky Mountain National Park

August 2011

The Energy quantum number determines how much diversity you can have. Energy-rich electrons can "buy" more “fancy” quantum states than energy-poor ones.

45

Shapes of atomic orbitals have to do with orbital angular momentum: go back and watch gyroscope YouTube.

http://www.albany.net/~cprimus/orb/

46

n=1, l=0, m=0

n=2, l=0, m=0

n=2, l=1, m=0

n=3, l=1, m=0

n=3, l=2, m=0

n=4, l=3, m=1

s-type p-type d-type (top)f-type (bottom)

Row 1 contains elements with only “low-energy” electrons.

47

if n = 1, then you can have l = 0 only.

Then you can only

have ml = 0. ms can

be +1/2 or - 1/2.

Aha! There are only two elements, H and He, on the top line of the periodic table.

Row 2: now some electrons (the ones that matter) have more energy.

48

if n = 2, you can have l = 0 or 1For l = 0, you can have m l

= 0 only. ms can be +1/2 or - 1/2.Check out Li and Be

For l = 1, you can have ml = 0 or +1 or -1For each of these three ml values, you can have ms = +1/2 or - 1/2 for a total of SIX states

Check out the six elements: B, C, N, O, F , Ne

Crayola Periodic Table

49

1s

2s 2p

3d3s 3p

4s 4p

Electron configuration problems are easy!

50

There are all kinds of mnemonic devices for this (see your textbook, CEF Study Guides, Virtual Book) but the easy solution is:

Just follow the periodic table!   Example: 

Calcium = 1s22s22p63s23p64s2

Why does Calcium behave rather like Barium?

51

 Because both end in s2

What does it mean?  The ending electron is the one with highest-energy.  This is the one that does the most work.  Its “workhabit” (orbital shape) is the same in calcium and barium.

If Donald Trump is in a hotel, he’s probablythe richest guest. Hotel assumes his personality.

Stop here?

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