1. Atomic Structure and The Periodic Table
Chapter 5
Atomic Structure and The Periodic Table

2. Unit 2 For Advanced Chemistry… For Chemistry…
This starts Unit 2, which will cover Chapter 5 and Chapter 28.
Unit 3 will cover Chapters 13 and 14 for those who like planning ahead.
For Chemistry…
You are going to do Chapter 5 totally, but only selected topics in Chapters 28, 13, and 14

3. Objective A http://sunsite. berkeley
Glenn T. Seaborg
A tour down memory lane from about 400 BC to the early 1900s…
For a quick recap on a lot of the amazingly important discoveries that brought chemistry from the land of con-men practicing mere magic tricks to the Central Science that it has become, see…
Chemical History PowerPoint, available in Unit 2 on the website.
Discovered Plutonium in 1940; won Nobel Prize in 1951; had dinner with Mr. Schwartz in 1981; element 106 named in his honor in 1997 (Sg); died 1999.

4. Objective B: Just how small is an atom. http://imagecache5. art
Has anyone been to a professional football stadium or a major college football stadium?
If the nucleus of an atom was the size of a marble, sitting at the 50 yard line, the electrons would be about the size of really little gnats (bugs) whizzing around the top rows of the upper deck.
So then, most of the atom is just “empty space.”

5. Objective B: Just how small is an atom. http://kara. allthingsd
Let’s use a penny as an example (picture, in slide show, is approximately life-size). A penny, if made of pure Cu (copper) would have 2.4 x 1022 atoms. That’s 24,000,000,000,000,000,000,000 atoms, btw.
If you lined up 100,000,000 atoms, they would make up a line of approximately 1 cm. So, 2.4 x 1022 atoms, if lined up would make a line that was approximately 2.4 x 109 KILOMETERS long.
Approx. 1 cm from arrow to arrow (in slide show mode)

6. How far is that?
2.4 x 109 KILOMETERS is 8 trips from the Earth to the Sun and back.
By the way, it takes just over 25 pennies (25.08) to make a mole of Cu. That’s grams of pennies.
Scanning tunneling microscopes are capable of seeing the surface of individual atoms. This is a relatively new development, within the past 20 years or so. Those didn’t exist when I was in high school or college.

7. Angstoms (Å) http://intro. chem. okstate
Even the largest atoms are very small. The diameter of a uranium atom is only about nanometers.
A special unit is sometimes used to describe atomic dimensions, such as atomic radius or atomic diameter. Note the trend as you go across a row and down a column.
That is the Angstrom. We use a Å to represent Angstroms (if you want to type that it’s shift-alt-A on a Mac and control-shift-2, shift-A on a bogus, inferior, Windows or Vista based machine).

8. Angstoms (Å) http://upload. wikimedia
Even the largest atoms are very small. The diameter of a uranium atom is only about nanometers.
0.345 nm = 3.45Å
1nm = 10Å
1Å = 1 x meters
A hydrogen atom is the smallest atom. H has a diameter of only 0.74Å. About 13.5 billion hydrogen atoms could fit onto the edge of a meter stick.
 Isotopes 

9. What does an atom look like. http://www. lanl
In your notes, draw a simple picture of an atom. How about Lithium.
What did you draw?
AAA baseball club Albuquerque Isotopes logo (you need to know what isotopes are!)

10. Atoms http://upload. wikimedia
Most people probably drew a nucleus of some type with electrons orbiting around it.
Possibly it looks a little like a mini solar system.
Atoms are composed of
Protons
Neutrons
Electrons
Neutron
Proton
Electron
Lithium
Planets=Electrons
Sun=Nucleus

11. Subatomic Particles Particle Relative charge Relative mass
(1 amu = mass of a proton)
Actual Mass of Particle
Proton +1
1 amu
1.67 x 10-24g
Neutron
Electron -1
0 amu
9.11 x 10-28g

12. Electrons Electrons were the first particle discovered.
JJ Thompson discovered the electron using cathode ray tubes, and modified the model of the atom because of this discovery.
The electron has a very small mass. It is actually 1/1840th the size of a proton ( times). In other words, if an electron was a smidge over a pound, protons and neutrons would weigh almost a TON.

13. Electrons http://educar. sc. usp
Robert Millikan measured the charge of the electron in “The Oil Drop Experiments”
This is what he used to do it…
Since it’s so small relative to a proton, we say that it has a relative mass of 0.
Electrons are negatively charged. Each electron has a charge of (Don’t forget the negative…it’s important!)
If an atom loses an electron, what remains will have a positive charge. If an atom gains an electron, it will have a negative charge.

14. Protons http://web.buddyproject.org/web017/web017/images/atom.JPG
Protons were the next subatomic particle to be discovered.
Protons were discovered by E. Goldstein.
Protons have a relative mass of 1 and a charge of +1.

15. Protons http://www.periodictable.com/Items/020.6/index.html
Protons determine the “identity” of an atom. The number of protons is a property called “atomic number.” Atomic numbers are on the periodic table.
The number of protons determines what kind of atom it is.
H has 1 proton
C has 6 protons
U has 92 protons
Atomic Number

16. Protons
Neutral atoms have the same number of protons and electrons. (Makes sense, right?)
The charges balance each other out. (Ca has 20 protons, and must have 20 negatively-charged electrons to balance out those positive charges)
Protons are located in the nucleus of the atom. (Where are the electrons?)

17. Neutrons http://www. ct. infn. it/~rivel/Archivio/chadwick
Neutrons are also located in the nucleus of the atom.
The nucleus was discovered by Ernest Rutherford, a former student of JJ Thompson.
The neutron was the last particle discovered, by James Chadwick, a former student of Rutherford.
Ooops, wrong neutron!
Chadwick

18. Neutrons
More than likely, the fact that neutrons had no charge made it harder to discover.
The neutron has a relative mass of 1, the same as a proton. However, it has no charge. Therefore, we say that the charge = 0.
The actual mass of a neutron is almost the same as that of a proton. It is slightly different
P = g
N = g

19. Golf Balls In Beakers My Little Model of the Atom http://www. vias
These are in the lab somewhere. Find them.
The pink balls represent protons.
The white balls represent neutrons.
Scientists quickly figured out by experimentation how many protons each element had. If you want to read more, check out the link above. Basically though….

20. Golf Balls In Beakers
They were able to ionize (remove electrons—all of them) and found that
Hydrogen had 1 proton. They figured this out because they were able to make H+ but not H2+
Helium had 2 protons. Again, they were able to make He+ and He2+ BUT NOT He3+
Lithium had 3 protons.
Magnesium had 12 protons.
Bromine had 35 protons.
Uranium had 92 protons. For the heavier elements, they were not able to remove all of the electrons. They had to do other experiments to figure that out, using a ratio of a known atomic number and an unknown one.

21. Golf Balls In Beakers
Not all the calculations were accurate at first, but they figured them out in time.
Scientists also knew what the masses of the elements were, and the numbers weren’t adding up.
Hydrogen was OK. It seemed to work out.
But helium should weigh twice as much as hydrogen. And lithium should weigh three times as much. And carbon should weigh 6 times as much.

22. Golf Balls In Beakers But they didn’t.
Helium was actually 4 times as heavy as hydrogen. Lithium was 7 times as heavy. Carbon was 12 times as heavy.
And that was very confusing. However, the neutron provided the final piece of the puzzle. The neutrons accounted for the missing mass.

23. Neutrons
It turns out that Helium has 2 protons AND 2 neutrons, which makes it 4 times as heavy as hydrogen.
Lithium has 3 protons and 4 neutrons, which makes it 7 times as heavy as hydrogen.
Carbon has 6 protons and 6 neutrons, which makes it 12 times as heavy as hydrogen.
The numbers added up.

24. The Nucleus http://www.chemicalelements.com/bohr/b0019.gif
Since the neutrons are located in the nucleus, with the protons, substantially ALL of the mass of the atom is contained within the nucleus.
Mass of nucleus in diagram g
Mass of electrons g
In other words, if the nucleus weighed 651 pounds, the electrons (combined) would weigh less than a McD’s quarter-pounder patty.
What element is this??

25. Strong Nuclear Force
But positively charged things repel other positively charged things, right?
Why do all the protons stick together in the nucleus?
Why doesn’t it just spontaneously break apart?

26. Strong Nuclear Force http://www. antonine-education. co
The answer is strong nuclear force.
It’s the strongest known force in the universe. It far, far stronger than gravity.
It only can be felt when the particles are extremely close together, like when they are packed together in the nucleus.
Protons and neutrons are made of quarks. It’s thought that the quarks attract other quarks and hold the nucleus together, even though all of the protons are positively charged and would otherwise repel each other.
The secret’s in the attractions between the quarks…

27. Objective D http://www.fiu.edu/~zhangj/cartoon_quantum3.gif
Scientists, starting with Dalton, came up with models of the atom, to help understand it and help to predict its behavior.
Check out the Chemical History power point for more details as the model evolved over about 130 years from Dalton to Quantum Mechanics.

28. Objective E
We already know that the number of protons is what makes an atom unique.
Hydrogen has 1 proton.
Carbon has 6 protons.
Uranium has 92 protons.
The “atomic number” is the number of protons. We sometimes use a Z to represent atomic number.
So, if “ProtonMan” was a superhero, he’d have a “Z” on his suit??

29. Objective E Find THEM!! So, for hydrogen, Z = 1 For carbon, Z = 6
For uranium, Z = 92.
What is the atomic number for
Aluminum
Zinc
Chlorine
Don’t memorize these…they are on the Periodic Table
Find THEM!!

30. Objective F
So, Z (atomic number) tells us how many protons an atom has. It does NOT tell you how many ELECTRONS you have (accurately) all the time!
Most atoms have no charge. That means that the number of protons (which are positively charged) must balance out the number of electrons (which are negatively charged).

31. Objective F
Unless you are TOLD that the atom has a charge, you should assume it has no charge, and therefore, # of protons = # of electrons.
Hydrogen (Z = 1) also has one electron.
Lithium (Z = 3) also has 3 electrons.
Carbon (Z = 6) also has 6 electrons.
Uranium (Z =92) also has 92 electrons.
BUT REMEMBER The numbers of protons doesn’t always equal the numbers of electrons.

32. Objective F
Some atoms can lose electrons. When they do so, they will form a positive “ion.” Some atoms can gain electrons. When they do so, they will form a negative “ion.”
An ion is a atom which has an electrical charge (either positive or negative). We’ll get to those in Chapter 6. Na+1 and Cl-1 are formulas for ions.
The number of protons cannot change. If the number of protons changes, it’s no longer the same element. Atoms can gain or lose electrons, but they can NOT gain or lose protons in any chemical reaction.

33. Schwartz’s Law (a law I made up…hey, it’s my class)
To calculate the number of electrons, use
# of Electrons = Z – IC
Where Z = atomic number and IC = ionic charge.
Ex: Suppose we have a sodium ion with a + 1 charge. How many electrons does it have? Atomic number (Z) is 11 (find this on Periodic Table) and ionic charge is 1.
# electrons = = 10

34. Schwartz’s Law Let’s calculate a couple more…
Ex: Suppose we have a sulfur ion with a - 2 charge. How many electrons does it have? Atomic number (Z) is 16 and ionic charge is -2.
# electrons = 16 - (-2) = = 18
Ex: Suppose we have an zinc atom with no charge. How many electrons does it have? Atomic number (Z) is 30 and ionic charge is 0.
# electrons = = 30

35. Objective F http://www.atomicarchive.com/Physics/Images/isotopes.jpg
6 neutrons
8 neutrons
How do we calculate how many neutrons we have?
In order to do that, we need to look at another property, called atomic mass. The atomic mass of an atom = THE SUM of protons and neutrons.
We will use another formula
# Neutrons = A – Z
A = Mass Number
So, what is Z again?
Hey these are isotopes again. Isotope = same # of protons but a different # of neutrons.

36. Objective F http://www.lbl.gov/abc/Basic.html#Nuclearstructure
Let’s look at an example. An atom of Bromine (Br-80) has Z = 35 and Mass Number = 80. How many neutrons does it have? (Br-80 doesn’t mean bromine with a charge of When they write it like that, it’s a DASH and 80 is the mass number)
# Neutrons = Mass Number - Atomic Number
# Neutrons = = 45

37. Objective F
Special note
Isotopes of hydrogen:
1H = hydrogen
1 proton, 0 neutron
2H = deuterium
1 proton, 1 neutron
3H = tritium
1 proton, 2 neutrons
Hydrogen is the only element with special names for isotopes.
An atom of Deuterium has Z = 1, and Mass Number = 2. How many neutrons does it have?
Since Z = 1, deuterium must be some type of hydrogen. Hydrogen has Z = 1, and since every element has a unique number of protons, no two elements can have the same number of protons.
Deuterium is a form of hydrogen. When deuterium reacts with oxygen it forms something called “heavy water.” Heavy water is represented with the formula D2O.
# of Neutrons = Mass Number - Z = = 1

38. Power Point Assignment
Pick an element…any element…
Well, not just any element. Pick an element whose symbol begins with the same letter as your first name.
If for some strange reason none exists, say for instance your name is Julie or Joe (sorry, no J elements) than use the next letter.
So Julie could pick Uranium
And Joe could pick Osmium
Research your element and write a 150 word summary on what you learned.

39. Objective G http://www. usagold. com/images/gold-coins-images
How do isotopes differ from each other? (You should know this by now).
Look at gold (Au) on the periodic table. It says that the mass = Since mass number and atomic number are ALWAYS whole numbers, how do we get .967?
The answer is that the atomic masses on the periodic table are averages.

40. Objective G
They get that average atomic mass for Au by taking into account ALL of gold’s isotopes.
Isotopes differ from each other in the number of neutrons. They behave the same CHEMICALLY because all isotopes of the same element have the same number of protons.
The study guide talks about water and heavy water. Heavy water is the same as water, except that instead of H-1 it is formed using H-2, which is sometimes called deuterium. So while water has a molar mass of 18, deuterium oxide or heavy water has a mass of 20 ( )

41. Objective G http://www.damninteresting.net/content/heavy_water_ice.jpg
Here’s an interesting fact…
Ice cubes made out of “heavy water” will not float. They sink to the bottom. So it has different physical properties.
Although it PROBABLY tastes the same, you should NOT drink it though. Too much of it can really mess up your system.

42. Objective G Don’t drink the HEAVY water!
You can purchase D2O. For $33 (for 2 ounces), you can purchase some from a company to be used as a “hydrating product” for your skin. It’s enriched with deuterium (meaning it has more in it than just normal water). It’s doubtful, in my opinion, that it does anything special, but if you have a different hypothesis, and $33 to burn, there’s a link in your study guide.
You can also purchase very pure heavy water as a scientific reagent. We call that deuterium oxide, because a real chemist would never order something that was called “heavy water.” It sells for $330 for 250g (which is about 2/3 of a can of soda). This stuff has been scientifically analyzed to contain 99.8% (at least) of D2O, which is why it’s a lot more expensive than the “hydrating product” for your skin.

43. Objective H How do we calculate the average atomic mass?
Math Alert
How do we calculate the average atomic mass?
To do so, you need to know 2 things:
All possible isotopes for an element
The percent abundance for each (in other words, how much of the whole is represented by each isotope).

44. Objective H Let’s look at an example: Chlorine has 2 isotopes
35Cl which is 75.77% of the total amount of chlorine.
37Cl which is 24.23% of the total amount of chlorine.
What is the average atomic mass of Chlorine?

45. Objective H
Cl-35 accounts for 75.77% of the total chlorine. CL-37 accounts for the rest.
Remember to convert percents into decimals, you have to move the decimal point 2 places to the left.
You then mutiply the percentage (in decimal form) times the mass number for that isotope. You do that for the other isotope too, and then add the answers together.
Avg Atomic Mass = 35 (0.7577) + 37 (0.2423).
Avg Atomic Mass = = 35.49

46. Objective H
In our class, we are always going to round average atomic masses to 1 decimal place.
So, we’ll round to 35.5 and that’s the average atomic mass of Chlorine that we’ll use.
Why can’t you just average 35 and 37 (the two isotopes) and get 36 as the average atomic mass? Why is that wrong?

47. The Periodic Table We’ve described the Periodic Table as
The biggest cheat sheet in science
The best tool we have in Chemistry
Your best friend on the test
Suppose we didn’t have a Periodic Table. You would have to memorize every fact about every element.

48. This is a map…

49. What does it tell you?
It shows you the states. If you know approximately where Virginia is, you can easily find it on the map.
It shows you state abbreviations. If you don’t know where Virginia is, or even what it sort of looks like, you can find it by using the abbreviation “VA.”
It shows you data for each state…
The name of the state capital.
The approximate location of the state capital
What other states are above, below or next to each state.
The sizes of the states..which are large and which are smaller.

50. What else does it tell you. http://www. destination360
Well, that’s about all, really.
But you can make some assumptions about the states based on their position on the map.
For example, VA borders NC, MD, TN, WV and KY. You might assume that VA has some things in common with each of these states.
You would be right.

51. Anything else? http://wwp.greenwichmeantime.com/images/usa/montana.jpg
You might also assume that Virginia doesn’t have much in common with WY, MT, ID or OR. All of these are large western states. How is Virginia different from these?
It’s smaller in terms of area. Montana is the 4th 147,000 mi2 and Virginia is 35th less than 43,000 mi2
It’s much larger in terms of population. Virginia is 12th largest with just over 7 million people. Montana is 44th largest with just over 900,000 people. To put that into perspective, four cities in Virginia (Virginia Beach, Norfolk, Arlington and Fredericksburg) have as many people as Montana.

52. What does this have to do with Chemistry?
Not a lot.
Except that the Periodic Table of the Elements is a lot like a map to guide you through Chemistry.
Like the US map, it divides the territory not into states, but elements. Elements that border other elements have more in common with each other than elements that are on opposite sides of the table.
If you can’t read a map, you might get lost on a trip. And if you can’t understand the Periodic Table, you might get lost on your trip through Chemistry.

53. Objective I
Suppose we didn’t have a Periodic Table. You would have to memorize every fact about every element.
You would have to memorize every symbol.
You would have to memorize atomic numbers.
You would have to memorize atomic mass.
You would have to memorize which elements behaved similarly to other elements.
And, a whole lot more.

54. Objective I http://chemheritage
That’s what scientists did for many years.
However, a Russian chemist named Dmitri Mendeleev changed all that for us.
He had the bright idea to try and organize all the known elements (back then, about 70 of them were known) into some kind of logical order.
Mendeleev didn’t know about atomic number. Protons hadn’t been discovered yet. However, he did know atomic mass. Soooo, he organized his table by atomic mass.
Dmitri Mendeleev

55. Objective I
Just putting them into some kind of logical order isn’t that much of an accomplishment. Many people could have done that. (In fact, others did, but prior to Mendeleev, no one got it exactly right.)
But Mendeleev left “holes” in the table to represent undiscovered elements. For example, the element under aluminum hadn’t been discovered yet. He called that eka- Aluminum. Eka was a prefix which meant below.
He also called the element under silicon eka- Silicon.
Nothing “fit” into the holes, so he left them blank, and he essentially challenged the rest of the world to find them.

56. Objective I
But many people could have left holes for “still undiscovered” elements. I’m still not that impressed. (Although to be honest, scientists at the time snickered at Mendeleev’s “boldness” in suggesting that his table would be correct, if only people would discover some new elements to put in the holes.)
But he went even further. Using his new table, he “predicted” that when those elements were discovered, they would have certain types of properties.
He predicted the boiling point, melting point, density, color, etc. And you know what: when eka-Aluminum was finally discovered, he was right!
OK, now that impresses me. That takes guts. Not only did he suggest that new elements would be discovered, but he even predicted how they would look and behave.

57. Objective I http://upload. wikimedia
Eka-Aluminum is actually Gallium (Ga). Eka- Silicon is Germanium (Ge).
That’s what Mendeleev did. And after the “holes” started to get filled in, just as Mendeleev had predicted, there was no more snickering.
But remember, the table was organized by atomic MASS, not atomic number.
After the discovery of the proton, another chemist, Henry Moseley, revised Mendeleev’s table slightly so that it was listed in atomic number order. That’s the table we have today.

58. Objective J http://www.dayah.com/periodic/Images/periodic%20table.png
Groups
Periods
A LITTLE PERIODIC GEOGRAPHY…
Rows on the Periodic Table are called PERIODS.
Columns on the Periodic Table are called GROUPS or FAMILIES

59. Objective J Group IA (1) = Alkali Metals
Group IIA (2) = Alkaline Earth Metals
Group VIIA (17) = Halogens
Group VIIIA (18 or 0) = Noble Gases
Group IB (Cu, Ag, Au) is sometimes called the Royal Family.

60. Objective J
Groups IA - VIIIA form the REPRESENTATIVE ELEMENTS (orange on my board)
Groups IB - VIIIB form the TRANSITION METALS (black on my board)
The two rows underneath the table are called the Lanthanides (top) and the Actinides (bottom; it was Glenn Seaborg who came up with the concept that the actinides behaved like the lanthanides).

61. Objective J The table can be divided into 4 blocks.
The “s block” is Group IA, IIA and He. (2 orange rows on left + Helium)
The “p block” is Groups IIIA - VIIIA (6 orange rows on right, not including Helium)
The “d block” is the transition metals (the black section)
The “f block” is the Lanthanides and Actinides.
The jagged line separates the metals from the nonmetals. Metals are to the left and are MOST of the table. Nonmetals are to the right. It’s important to know what’s a metal and what’s not.

62. Objective J
Some of the elements along the jagged line are a special case called metalloids.
B, Si, Ge, As, Sb, Te and Po are metalloids. Metalloids behave like metals in some ways, but also like nonmetals in some ways.

63. Na
Find Na on the table.
Na stands for sodium. Sodium is one of those elements that we’re going to use over and over this year. Might as well memorize it now.
Of course that makes no sense, unless you know that the Latin name for sodium is natrium, and then it makes a lot more.
Why did we give it a Latin name? Well, this British guy named Sir Humphry Davis gave it that name back in when he discovered it.

64. K
Right underneath sodium is K or potassium. Ok, does that have a Latin name too? Yes, Sir Davis discovered this too and he named it kalium.
Why? I don’t know but the guy that discovered it got to name it and that’s what he decided to name it.
Based on your understanding of maps do you think K has a little or a lot in common with Na?

65. Alkali Metals
Sodium and potassium and all the rest of the elements in that group are alkali metals.
The alkali metals all have one valence electron. That similarity is what makes them behave the same chemically.
They are very reactive. Reactivity is highest on the outer edges of the table and elements get less reactive the closer they are to the center of the table. Lithium is the least reactive alkali metal and reactivity increases as you go down the group.

66. Noble Gases
The noble gases are very stable. They are unreactive because they are so stable.
The noble gases all have 8 valence electrons. Helium is an exception in that it only has 2.
The noble gases are obviously gases at normal room temperature.

67. Alkaline Earth Metals & Halogens
Group IIA or Group 2 are called “the alkaline earth metals.” They have 2 valence electrons.
Group VIIA or Group 17 are called “the halogens.” The halogens all have 7 valence electrons, and like the alkali metals, they are very reactive (fluorine is most reactive and reactivity decreases as you go down the group).

68. Customize your table Highlight the s block in BLUE
Highlight the p block in ORANGE
Highlight the d block in YELLOW
Highlight the f block in PINK
Circle the element symbols for the gases.
Draw a square around the symbol for Hg and Br. These are the only 2 liquids at room temperature.
Put a * in the box for H, O, N, Cl, Br, I, and F. These are diatomic elements.
As you learn more, continue to customize your periodic table.

69. Power Point Assignment http://sciencespot.net/Media/ptablebasics.pdf
Get the Periodic Table Basics Assignment from me. (I found this assignment at sciencespot.net, and special thanks to Tracy Trimpe for not having to reinvent this wheel.)
Do the assignment. You will turn in the questions on the back PLUS a simplified version of the Periodic Table that you will make in the assignment.
To do this assignment, you need to know what a Bohr Diagram is and what a Lewis structure is.
Continue on to find out.

70. Power Point Assignment
A Bohr diagram shows the electrons in “energy levels.”
The energy levels are represented by circles. The inner most circle can have 2 electrons. The other outer circles, can have a total of 8 each.
You represent the electrons with a dot, starting on the inner circle, filling that up, and then moving outward. You must fill the circle completely before you can move to the next circle.
The assignment gives you an example using Boron.

71. Power Point Assignment
Once you have the Bohr diagram done, the Lewis structure is very easy.
You represent only VALENCE electrons on the Lewis structure.
Valence electrons are electrons which are in the highest occupied energy level. In other words, the electrons in the outermost circle in your Bohr diagram are valence electrons.
They give you an example using Boron. B has 3 electrons in the outer circle, so the Lewis structure has 3 dots.

72. Power Point Assignment http://www.ausetute.com.au/lewisstr.html
A Lewis structure can have a maximum of 8 dots.
You put one dot on each side of the symbol (top, bottom, left and right), until each side has a dot.
Then you can start pairing them up, until every side has 2 dots.
When every side has two dots, you can’t put any more dots on the structure. If you need to, you did something wrong.
Oxygen
Lewis structure

73. The End Next you should look at the Chemical History power point.
Then…
Advanced Chemistry should go to Chapter 28 powerpoint.
Chemistry should go to the Special Topics for SOL 2
powerpoint.