Romantic Atomic Love Affairs?

5

http://www.youtube.com/watch?v=L4w1Mp6Mce4&feature=related

http://www.youtube.com/watch?v=6nclUZoouHQ

Trivia: besides LSU, what university sings Hey Baby at games?

Love isn’t always romantic.

Atomic dating is more often needy, fast and brutal,the surroundings messy and cheap.

Hotel Californian—Santa Barbarahttp://www.edhat.com/img2/beats/HC-006.jpg

Electrons exist in orbitals. We can think of these as Bohrbits…Standing Waves in 3

Dimensions.

8

Of course 2-D is easier to see. Sand on a kettle drum! By this analogy, electrons would be where sand isn’t(sand sits at the nodes).

Bohrbits: More energy can afford more complexity. These are standing waves in three dimensions.

9http://chemlinks.beloit.edu/Stars/images/orbitals.jpg

Crayola Periodic Table

1s

2s 2p

3d3s 3p

4s 4p

Coulomb's Law: opposites attract. 

2r

qqF

F

+

-

+

-Slow, low-E electron

Fast, high-E electron

Small radius

Big radius

Electron Configurations: how are electrons partitioned according to energy?

But first a romantic (?) Southern riddle about Billy Joe and Annabelle Leigh*

*With apologies to Edgar Allen Poe

Mendeleev was even able to predict!

One example: Eka-silicon (Ge)Predicted 1871 Discovered 1886

At.Wt. 72 72.6Color gray grayDensity 5.5 5.5(g/cm3)

Oxide EsO2 GeO2

Chloride EsCl4 GeCl4

B.P. Chloride Under 100 84(oC)

Meyer also saw periodicity. His version was physical—we can imagine it was size-based.

But how do we know this???

Other things that repeat•Density •Boiling point •Melting point •Ionization energy (e.g., how hard to yank an electron away) •Which way do you think ionization energy goes?  

22

It is hard to steal electrons from the elements on the right side of the periodic table.

•Define: the "desire" an atom has for electrons•All atoms desire electrons—a matter of degree •Atoms at the very right of the table (with completely full shells) don't want to acquire more electrons. •Atoms near the right of the periodic table (with almost full shells) want electrons very badly. We say these atoms (like chlorine or fluorine) are electronegative. •Atoms on the left are glad (well, not too sad) to give them up.

Electronegativity

1. The most electronegative atom is F.2. Electronegativity is yet another thing that

repeats.

Major groups: most elements are metals!

Group VIII are the Noble Gases

•Too regal to react

•All end in s2p6 ***

•Example: Argon =

1s22s22p63s23p6

***Except He (1s2)

                                

“We are not amused.”

Group I and Group II = Metals

Alkali metals, example Sodium 

not greedy at all—ready to lose electrons—its last electron was high-energy and “out there” ready to get stolen!        

Na = 1s22s22p63s1

Mg = 1s22s22p63s2

28

Group VII = Halides Example: Chlorine very greedy:

Chlorine: 1s22s22p63s23p5

29

Transition metals: electrons galore, but not desperate to get rid of them—lots of protons to hold electrons where they are. example Iron: 

--Sea of electrons--certainly enough electrons to conduct electricity

--but not desperate to get rid of themFe: 1s22s22p63s23p64s23d6

Metalloids example Silicon:  can be "doped" to behave a little bit like metals; semiconductors

Nonmetals example Carbon:  share and share alike C: 1s22s22p2

Si: 1s22s22p63s23p2

http://1.bp.blogspot.com/_Zx0SO3YqO2g/TCGo5P6JawI/AAAAAAAAAA8/sdLBzI2Fep4/s320/Transistor.jpg

Octet Rule: Chemistry often follows the rule of 8’s: Atoms try to end in s2p6

•Rule of 8's: the s2p6 configuration is very stable: noble gases

•Atomic jealousy: every atom wants to look like s2p6--e.g., Na   Na+1 

•Why?---What is special about s2p6? Is there an easy answer?

Who is more likely to encounter extra-terrestrial life, you or one of these people?

We repeat: electrons that are “out there” are more energetic…and more likely to be found by other atoms.

+

-

+

-Slow, low-E electron

Fast, high-E electron

Valence Electrons = Energetic, Outer Electrons

The active electrons are called valence electrons. 

Inner shell electrons are “screened”—not so visible to alien atoms.

Examples:  Potassium has 19 electrons, but only 1 valence electron

Carbon has 12 electrons, but only 4 valence electrons

The number of valence electrons = the Group Number!

Lewis Dot Structuresshow just the valence electrons

By Octet rule, Chorine would rather be this anion: -1

Preview

Cl2, O2, N2 examples

Na & Br example

Don’t worry, we’ll get LOTS more covalent examples

later!

Coulomb's Law:  Can we explain Meyer’s size trends, ionization energies &

electronegativity? 

2r

qqF

F

Compare Cl and Na

Cl has q+ = 17Na has q+ = 11

Cl pulls harder on its electrons than Na. So….Cl will steal fromNa…and put the electron in a smaller orbital, too, closer to nucleus.

See? Cl is smaller. And Ar is smaller still.

Then why does K get bigger again?

More energy! K’s last electron has energy quantum number n=4

The last electron captured by the K nucleus was a fast, energetic one.

The last electron placed determines what the atom wants to do.

Types of Bonds: Quick Intro

Ionic Bonds: back to the legend of Billy and Annabelle LeighDefine: An ion is an atom or molecule that carries a net charge. Cation = + ion (lost an electron) Anion = - ion (gained an electron)

Anions attract Cations

Billy Joe pulls a wig out of his pocket, gives to Annabelle Leigh. Then they can snuggle.

Billy Joe Cation

Annabelle Leigh Anion

Why do ions form?

Why do ions form?

The public debt of the U.S. is calculated to the penny!

March 1, 2005: $7,701,629,503,518.55 October 5, 2011: $14,837,099,271,196.71

Your share: about $47,400It goes up by about $13/day/person

45http://www.usdebtclock.org/

Electrons & Protons do an even betterbalancing act. Balance to better than… 1 : 1,000,000,000,000,000,000,000,000

+ +

Fcoulombic for 1% imbalance of charges would lift Earth in its own gravity (from Feynman Lectures)

46

Isoelectronic = Same Electronic

Configuration

Ne / Na+ / Mg++

47

A Note About NotationMg++ means the same thing as Mg2+  

Either is very different from something like Mg2

+   (not a normal form of magnesium)

DOWN (SUBSCRIPTS) =  how many atoms

UP (SUPERSCRIPTS)  = how many charges

48

Left subs/supers vs. Right subs/supers

12

2211

Naprotons

protons +neutrons

electroniccharge

how many

49

Oxidation means losing electrons.

We have seen cases where atoms give up electrons to form cations.

This is an example of oxidation.

Where do such electrons go?

Reduction:gaining electrons

50

Example: chloride anion

Consider the case where chlorine gets reduced (gains an electron)  Cl = 1s2 2s2 2p6 3s2 3p5 Cl + e- Cl-

51

Let’s do another, more highly charged, anion

N = 1s2 2s2 2p3

Let it gain three electrons to become nitride:

                                

52

Suppose we repeat with Mg and F

Mg Mg2+ + 2e-

2e- + 2F 2F-

Mg + 2F MgF2

It takes TWO Fluorines to soak up the TWO electrons from the ONE magnesium.

Uh-oh….Here is our first atomic “three-way.”

54

One oxygen could serve same "soakup" function as 2 fluorides.

Mg Mg2+ + 2e-

2e- + O O2- _____________________________________ Mg + O MgO Magnesium Oxide

55

Let’s do Na and N

Let’s do Ca and N

56

Na and N answer

3 Na 3Na+ + 3e-3e- + N N3- ______________________________________ 3Na + N Na3N Sodium nitride

57

Ca and N answer

Ca Ca2+ + 2e-

3e- + N N3-

Doesn't balance!Multiply top by 3 and bottom by 2

3 Ca 3Ca+2 + 6e-6e- + 2N 2 N3- ___________________________________________ 3Ca + 2 N Ca3 N2 Calcium nitride

58

Here’s a trick for predicting ionic compounds from the periodic table (Life and Chemistry are both full of tricks!)

•Count how many electrons the metal must lose to become like a rare gas. (2 for calcium).

•Give this number to the nonmetal.

•Count how many electrons the nonmetal must gain to •become like a rare gas. (3 for nitrogen)

•Give this number to the metal.

59

What do Si and O make?

What do Al and O make?

What do Fe and O make?(uh-oh)

60

Breaking Ionic Bonds……..can be as simple as adding water

NaCl Na+ + Cl-            H2O

Sometimes, it is much harder….

e.g., Al2O3

61

Covalent Bonding is The Gray Area of Electron Accounting

Not everything is black and white like the all or nothing electron transfer of ionic bonds.

Ionic bonds can't explain molecules like Cl2.

Both atoms in a Cl2 molecule want the electrons equally.

....But the octet rule still can!  

62

Think of atoms like people:

Ionic People Matching Set

             

Oxygen, Fluorine

Potassium, Cesium

63

Covalent People

CarbonSilicon

64

65http://www.funnyanimalpictures.net/data/media/1/skinny-cat-dance.gif

http://media.photobucket.com/image/fat%20cat/misscole1o1/Internet%2520Pictures/FatCat.jpg

Sample Covalent Bonding

66

Let’s do oxygen, O2

67

Oxygen Answer

68

2 covalent electrons in

one orbital = 1 covalent bond

69

Do Nitrogen, N2

70

Astaxanthin, a member of the carotenoid family, is part of a nutritious diet—for lobsters and shrimp. These crustaceans bind astaxanthin to the protein β-crustacyanin, which changes the shape of the astaxanthin molecules, turning them a gray-blue color. Cooking releases the molecules, returning them to their original bright red color.

cook

Q. Are we ready for complex covalent molecules yet?A. Almost.

71

72

73

74

75