1. OB: intro to understanding the Periodic Table
1. A salute to Dimitri Mendeleev

2. 1817 — Bavarian chemist Johann Döbereiner developed the law of triads where, for example, lithium, sodium, and potassium displayed similar properties.
1862 — French geologist Alexandre-Emile Béguyer de Chancourtois’ proposed a system ordered by increasing atomic weight and with similar elements lined up diagonally in a cylinder.
1863 — English chemist John Newlands classified the elements into 11 groups, based on similar physical properties. He noted that there existed many pairs of elements, which differed by multiples of eight
the law of octaves.
1869 — Russian scientist and educator Dmitri Mendeleev unveiled the hidden order of the natural world by developing the comprehensive periodic table—combining the law of triads, octaves, and diagonals. He surprisingly and boldly included "holes" in his table for as yet undiscovered elements and he even had the audacity to predict their properties!

3. You should memorize the names of the groups of atoms on the table.
In our class, poor metals are other metals, or transitional, the rare earth are the inner transitional
You should memorize the names of the groups of atoms on the table.

4. 4. The up and down columns of the periodic table are the GROUPS.
5. Atoms in the same group share many similarities of chemical properties, because they have similar electron orbitals, which means they will bond in similar ways.
Look at group 1, lithium, sodium, and potassium.
6. How will they each bond with chlorine, with oxygen, or with phosphorous?
Li + Cl
Li + O
Li + P
Na + Cl
Na + O
Na + P
K + Cl
K + O
K + P
RATIO

5. Note how each metal bonds in the same ratio with chlorine, and then a different ratio with oxygen, and a third ratio with phosphorous.
Each of the group one metals is similar in that it has 1 valence electron, so they all will make similar ionic bonds.
Li + Cl
LiCl
Li + O
Li2O
Li + P
Li3P
Na + Cl
NaCl
Na + O
Na2O
Na + P
Na3P
K + Cl
KCl
K + O
K2O
K + P
K3P
RATIO
1:1
2:1
3:1

6. 7. In group 18, all the gases are called “noble” because they do not make bonds with other atoms. They are nearly inert!
8. Group 2 metals all have 2 valence electrons, they too bond in similar ways.
9. Atoms in groups are similar in chemical ways.
10. Groups go up and down.
11. Our periodic table has 18 groups.

7. 12. The periods of the table go left to right.
14. The periods contain many elements that have little similarities.
15. Period numbers are , and they correspond to the number of electron orbitals in the atoms of that period.
16. Fill in the chart:
What are the electron configurations of the first four elements in groups 3 + 4?

8. Group 3 elements all have three orbitals Na Mg Al Si
2-8-1
2-8-2
2-8-3
2-8-4 K Ca Sc Ti
Group 4 elements all have four orbitals
17. Quick check: what’s the electron configuration for Fr Francium # 87

9. which is a total of 7 orbitals, which is good since Fr is in period 7
18. How many protons, neutrons, and electrons are in an atom of zirconium?

10. Zirconium - 40
That’s 40 protons
And 40 electrons (since the positives = the negatives)
And because…
Atomic mass = protons plus neutrons, and atomic number = the number of protons
Atomic Mass of zirconium = which rounds to 91
91 – 40 = 51 neutrons

11. 19. Demetri Mendeleev created the first real, modern style periodic table, one that you might recognize, just after the American Civil War, around 1869.
This was not a small task.
He literally took almost one hundred known substances thought to be elements, and figured out a way to put them into one table so that their properties all made sense.
That is, some properties, but which ones?
Which elements were missing? One, two? More? Where to start?
Which properties are more important than others? Wow!

12. 20. What does that Periodic part even mean here?
We will look at several properties of the elements and how this puts them into particular places on the table.
We’ll watch how these properties change as you move down the table, or across the table.
Even the name of this table is important: The Periodic Table of the Elements.
20. What does that Periodic part even mean here?
Did you ever even give that word a thought?

13. 21. The elements of the Periodic Table are arranged in order of increasing atomic number, and by doing this, the properties of the elements will periodically repeat themselves.
That means: by keeping the atoms in this order of atomic number (number of protons and number of electrons), in this shaped table, the elements that all bond in similar ways will be in the same groups, and the atoms with the same number of electron orbitals will all be in the same period.
You just wait for the Periodic Table Puzzle Lab. The complexity of Mendeleev’s thoughts are astonishing, and were literally shocking in their perfection.
He predicted that several elements were not yet found, because of the way the properties aligned, he “knew” that other elements belonged on the table he constructed, but he did not have them.
He told scientists: go find me the missing ones, here are their properties!

14. Within the table there are many trends of properties.
We will look at some of these trends this week. The easiest trend to see is atomic mass.
To determine the group trend for atomic mass we’ll look at atomic mass of four elements in two different groups. Let’s look up the atomic masses for group 2 + group 17:
Group 2
Atom
mass Be Mg Ca Sr
Group 17
Atom
mass F Cl Br I

15. It should be clear that going down these and all the groups of the periodic table, that the atomic mass gets larger (because the atoms get larger.
To state this properly: The group trend for atomic mass is increasing.
Group 2
Atom
mass Be
9 amu Mg
24 amu Ca
40 amu Sr
88 amu
Group 17
Atom
mass F
19 amu Cl
35 amu Br
80 amu I
127 amu

16. 25. This time let’s do the period trend for atomic mass, we’ll examine period 3 and 4.
Remember, whenever possible, use 4 atoms in a row to measure a trend.
atoms Na Mg Al Si
masses
atoms K Ca Sc Ti
masses

17. 26. How can we state this trend???
This time let’s do the period trend for atomic mass, we’ll examine period 3 and 4.
Remember, whenever possible, use 4 atoms in a row to measure a trend.
atoms Na Mg Al Si
masses
23 amu
24 amu
27 amu
28 amu
atoms K Ca Sc Ti
masses
39 amu
40 amu
45 amu
48 amu
26. How can we state this trend???

18. 26. The period trend for atomic mass is increasing.
When ever you state a trend, it’s always a complete sentence. It’s always starts with “The period trend…” or “The group trend…”.
The statement ends with is “increasing” or “decreasing”.
It’s easy, the rules are clear. Memorize the way to do this, but not the trends. The trends are right on the table to figure out every time you need them. Always use 4 atoms in a row to measure a trend.

19. OB: Trends of the periodic table. (atomic mass + atomic size)
Periodic Table Class #2
OB: Trends of the periodic table (atomic mass + atomic size)
27. Trend: A general pattern or tendency; consistent and repetitive
28. On the periodic table there are many periodically repeating patterns.
29. The table itself is arranged in order of increasing atomic number (which is the number of electrons = the number of protons.
30. There are group trends (that follow a pattern going down groups).
31. There are period trends (that follow a pattern going across periods).
We’ll start to examine these patterns now.

20. It should be clear that going down these and all the groups of the periodic table, that the atomic mass gets larger (because the atoms get bigger).
Group 16
Atom
mass O
16 amu S
33 amu Se
79 amu Te
128 amu
Group 2
Atom
mass Be
9 amu Mg
24 amu Ca
40 amu Sr
88 amu
To state this properly: The group trend for atomic mass is increasing.

21. 33. The period trend for atomic mass in increasing.
This time let’s look at the period trend for atomic mass, we’ll examine period
Remember, whenever possible, use 4 atoms in a row to measure a trend.
atoms Na Mg Al Si
masses
23 amu
24 amu
27 amu
28 amu
atoms K Ca Sc Ti
masses
39 amu
40 amu
45 amu
48 amu
33. The period trend for atomic mass in increasing.

22. That’s one trillionth of one meter. With a “T” - a Trillionth!
Trend #2 Atom Size (atomic radius in picometers)
34. How big is a picometer?
A meter is a basic unit of length in the metric system.
A picometer is 1 x of one meter, or:
35. One picometer = 1 pm = m
That’s one trillionth of one meter.
With a “T” - a Trillionth!
Really, really tiny, but NOT ZERO.

23. 37. Group trend for atomic radius:
36. Using four atoms in a row from groups 1 and 17, determine the group trend for atomic size, and state it in one sentence in proper form.
Group 1
Atom
radius Li Na K Rb
Group 17
Atom
radius F Cl Br I
37. Group trend for atomic radius:

24. The group trend for atomic radius is increasing.
36. Using four atoms in a row from groups 1 and 17, determine the group trend for atomic size, and state it in one sentence in proper form.
Group 1
Atom
radius Li
130. pm Na
160. pm K
200. pm Rb
215 pm
Group 17
Atom
radius F
60. pm Cl
100. pm Br
117. pm I
136 pm
The group trend for atomic radius is increasing.
37. Group trend for atomic radius:

25. 38. Why is the group trend for atomic radius size increasing?
THINK!!! Who has an idea that’s clear?

26. Each period number increase is an increase of orbital number.
38. Why is the group trend for
atomic radius size increasing?
Because each time you go lower in the group, the atoms are adding orbitals.
Each period number increase is an increase of orbital number.

27. K Ca Sc Ti Rb Sr Y Zr 40. State the period trend for atomic radius.
39. This time we’ll examine the period trend for atomic radius using the first 4 atoms of period 4 and of period 5.
Period 4 Atoms K Ca Sc Ti
Radius in pm
Period 5 Atoms Rb Sr Y Zr
Radius in pm
40. State the period trend for atomic radius.

28. Period 4 Atoms K Ca Sc Ti
Radius in pm
200.
174
159
148
Period 5 Atoms Rb Sr Y Zr
Radius in pm
215
190.
176
164
40. The period trend for atomic radius is decreasing!

29. Although counter intuitive, this is true and the reason will open your minds up some. Think now…
What is the same for each atom in a period? What changes or is different?
How do we explain this trend?

30. What's up with that? Atom: Rb Sr Y Zr 4 37 38 39 40 215 190 176 164
41.
What's up with that?
How could the atomic radius decrease as you go across the period?
What do these atoms have changing that could affect that?
Let’s look at period 4 to start:
Atom: Rb Sr Y Zr
# of orbitals 4
# protons 37 38 39 40
Radius in pm
215
190
176
164

31. 42. Going across a period, each atom has the SAME NUMBER OF ORBITALS for the electrons, but each successive atom has ONE MORE PROTON, pulling harder and harder on those negative electrons in this 4th orbital.
43. The nucleus becomes increasingly more positive, the inward pull on the electrons becomes greater and greater, making the atomic radius shrink.

32. 44. The Trend for Atom Size.

33. Co Ni Cu Zn 45. What happens with the atomic radius of
Co, Ni, Cu and Zn?
Look at those atomic radii now.
Atom: Co Ni Cu Zn
Atomic radius in pm

34. Atom: Co Ni Cu Zn
Atomic radius in pm
118
117
122
120.
If the period trend for atomic radius is decreasing, how can copper be bigger than cobalt nickel?
46. How can zinc be bigger than cobalt and nickel?

35. Atom: Co Ni Cu Zn
Atomic radius in pm
118
117
122
120.
If the period trend for atomic radius is decreasing, how can copper be bigger than cobalt nickel? How can zinc be bigger than cobalt and nickel?
46. Trends are patterns that are regular + predictable, but not the law.
These are exceptions to the trend. You already know a few another “exceptions to a trend”. The AlPo dog food exception to the metalloid “rule”.

36. Trends of the Periodic Table Class #3
Our Investigation Into
Net Nuclear Charge Trends
Metallic + Non-Metallic Property Trends
1st Ionization Energy Trends. 
Take out your periodic tables now.

37. Net Nuclear Charge is very easy to “get”
Net Nuclear Charge is very easy to “get”. Once you get passed the definition of what the heck it is, you’ll understand.
Your NET WORTH is the SUM of your cash and assets, take away all your liabilities or debts. The positives and the negatives combine to your NET worth.
The net sum of these is your NET WORTH.
47. The NET NUCLEAR CHARGE means, what is the net sum of all the charges in the nucleus of the atom you are measuring?
48. Before we do calculations, what particles are in the nucleus? What are their charges?

38. He Li Cu Hg Fr 49. Fill in this chart. Net nuclear charge
Every atom’s nucleus has just protons (positive charges) and neutrons (no charges).
The sum of positive charges with neutral charges is always positive.
The NET NUCLEAR CHARGE for any atom is that atomic number, with a + sign.
49. Fill in this chart.
Atom
Atomic number
Net nuclear charge He Li Cu Hg Fr

39. He 2 +2 Li 3 +3 Cu 29 +29 Hg 80 +80 Fr 87 +87 Net nuclear charge
Every atom’s nucleus has just protons (positive charges) and neutrons (no charges).
The sum of positive charges with neutral charges is always positive.
The NET NUCLEAR CHARGE for any atom is that atomic number, with a + sign.
Fill in this chart quickly
Atom
Atomic number
Net nuclear charge He 2 +2 Li 3 +3 Cu 29
+29 Hg 80
+80 Fr 87
+87
That was easy!

40. 50. What is the group trend for net nuclear charge?
51. What is the period trend for net nuclear charge?

41. 50. The group trend for net nuclear charge is increasing.
What is the group trend for net nuclear charge?
What is the period trend for net nuclear charge?
50. The group trend for net nuclear charge is increasing.
Because you keep adding more and more protons (more positives) and more and more neutrons (who cares?)
51. The period trend for net nuclear charge is increasing.
Because you keep adding more and more protons (more positives) and more and more neutrons (who cares?)

42. 52. The net nuclear charge for any atom is always that atom’s atomic number with a + sign.
The nucleus of any atom contains a certain number of positive protons an, an irrelevant number of neutral neutrons for net nuclear charge. (neutrons have NO charge).

43. 53. Metals are atoms with certain properties
53. Metals are atoms with certain properties. They are on the “left” side of the table.
54. Non-metals are atoms with other properties, they are on the “right” side of the table.
55. Metal Properties include: being malleable and ductile, have the ability to conduct heat and electricity, they form cations not anions, they are shiny (have luster), they are dense, they have lower specific heat capacity constants, etc.
56. Non-metal Properties include: not being malleable or ductile (they are brittle or not even solids), not conducting heat or electricity well, they only form anions (the noble gases don’t form ions at all), they aren’t lustrous (most are gases!), they are less dense and usually have higher specific heat capacity constants.

44. We won’t do this, but you can be assured someone has, and if you were to make a measure and compare all the metals together in every category, which one would have the most luster, and the most cation forming ability, and be best in all the other ways?
57. The most metallic element is francium In fact, the easy way to “know” which metal is more metallic than other metals is by its proximity to Fr on the table.
The closer a metal is to the bottom left corner of the table, the more metallic it is.
For example, which metal is more metallic: Ta or Au?
Which metal is more metallic Sn or Au?
This is too easy!
58. The most non-metallic of all is helium. The closer on the table an atom is to helium, the more non-metallic like it’s qualities.
Which is more nonmetallic: Cl or B? How about Ar or Rn?

45. The most-metallic trend and the most-nonmetallic trend is the second dumbest thing I teach you all year. Believe it or not, something is even less valuable than this particular tidbit and is still to come!
Metallic properties are important, as are the nonmetallic properties. Which atoms are metallic, or less metallic is interesting. To just accept that Fr is the “most metallic of them all” when very few atoms of it have ever even been isolated, or to somehow evaluate that helium is “more inert” than neon, and that this is something valuable enough to MEMORIZE, well that is bullpucky.
Chem is great, the state of New York means well, but a few times a year there is true idiocy to help you make sense of things.

46. First Ionization energy is more tricky because it has a funky definition.
First, the unit is kilojoules per mole. It is a measure of how much energy it takes to do something.
If you had a mole of sodium atoms (23 grams) and wanted to have instead, one mole of Na+1 cations, those electrons don’t just fall off. You have to take them off.
Check table S, how much energy does this take?

47. 59. Define 1st Ionization energy
The amount of energy required to remove one mole of outermost (valence) electrons from one mole of an atom is called the first ionization energy. Or
59a. The amount of energy required to form a 1st order cation (a +1 cation).
Not all metals like to be +1, like calcium which would make a +2 cation.
60. There is also 2nd ionization energy, and 3rd too. They’re not in our class.
This is a definition only, and trend only bit of information in our level of chem.
Some atoms “like” to lose electrons, such as metals. Nonmetals do NOT like to become positive ions, but if you’re willing to invest the energy required, you could.

48. To remove a mole of electrons from a mole of sodium atoms takes 496 kJ/mole.
62. Your mission, if you choose to accept it, fill in the charts here, determine the group trend for 1st Ionization energy and the period trend for 1st ionization energy now.
Group 1 atom
1st ionization energy Li
kJ/mole Na K Rb

49. To remove a mole of electrons from a mole of sodium atoms takes 496 kJ/mole.
Your mission, if you choose to accept it, fill in the charts here, determine the group trend for 1st Ionization energy and the period trend for 1st ionization energy now.
Group 1 atom
1st ionization energy Li
520. kJ/mole Na
496 kJ/mole K
419 kJ/mole Rb
403 kJ/mole
63. It apparently gets “easier”, or takes less energy to remove a whole mole of valence electrons as you move down a period. WHY???

50. Electron configuration
To remove a mole of electrons from a mole of sodium atoms takes 496 kJ/mole.
Your mission, if you choose to accept it, fill in the charts here, determine the group trend for 1st Ionization energy and the period trend for 1st ionization energy now.
Group 1 atom
1st ionization energy
Electron configuration Li
520. kJ/mole
2-1 Na
496 kJ/mole
2-8-1 K
419 kJ/mole Rb
403 kJ/mole
63. Because: Their valence electrons just keep getting FURTHER and FURTHER from the positive nucleus, they are just easier to pull off the atoms.

51. In Lithium, the outermost electron is in the 2nd orbital.
In sodium, the outermost electron is in the 3rd orbital.
In every atom going down a period, the outermost electron that would be removed is further and further away from the positive nucleus.
It takes less and less energy to pluck off those outermost electrons from bigger and bigger atoms going down each group.
64. The group trend for 1st ionization energy is decreasing.

52. Period 2 Li Be B C N kJ/mole Period 5 Rb Sr Y Zr Nb kJ/mole
65. Time to figure out the period trend for 1st ionization energy. Let’s use period 2 and period 5 (five atoms in a row from each…
Period 2 Li Be B C N
kJ/mole
Period 5 Rb Sr Y Zr Nb
kJ/mole

53. Period 2 Li Be B C N kJ/mole 520. 900 820 1086 1402 Period 5 Rb Sr Y
65. Time to figure out the period trend for 1st ionization energy. Let’s use period 2 and period 5 (five atoms in a row from each…
Period 2 Li Be B C N
kJ/mole
520.
900
820
1086
1402
Period 5 Rb Sr Y Zr Nb
kJ/mole
403
549
600.
640.
652

54. 66. It’s clear that there is an exception in the 2nd period, but the period trend for 1st Ionization energy is increasing.
Why?
What’s going on inside these atoms that makes this energy demand drop going across the table?
For the same reason that the atoms get smaller going across the table (same number of orbitals, more and more protons in the nucleus pulling tighter and tighter), the outer electrons get harder and harder to pull off.

55. 67. The group trend for 1st Ionization energy is decreasing, because removing the outmost electron gets easier as the electrons move further from the nucleus.
68. The period trend for 1st Ionization energy is increasing, because removing the outmost electron gets harder as the electrons move closer to the nucleus. This happens because the atoms of a period all have the same number of electron orbitals, but more and more protons. As they get physically SMALLER in radius, their electrons are harder to remove because the electrons are closer to the nucleus.

56. Sounds like a lot, but it will take 10 minutes at most.
Tonight,
please do HW
Sounds like a lot, but it will take 10 minutes at most.

57. Trends of the Periodic Table Class #4
Cation Size, Anion Size

58. That’s a lot to ponder, but it’s easy enough. Here goes…
69. The group trend for atomic size (atomic radius) for both metals and nonmetals is increasing, because each atom lower in the group has an additional orbital.
The more orbitals that you have, the bigger you are.
There are no picometer measures for cations (or anions) so we will evaluate this trend by examining the electron configurations and take into consideration the numbers of protons that they have. We’ll ponder the number of protons pulling on the number of electrons in each ion.
That’s a lot to ponder, but it’s easy enough Here goes…

59. 70. Determine the group trends for cation size
70. Determine the group trends for cation size. Then the group trend for anion size as well.
Group 1
cations
Group 1 cation electron configurations
Li+1
Na+1
K+1
Rb+1
Group 17
anions
Group 17 anion electron configurations
F-1
Cl-1
Br-1
I-1
71. State the group trend for cation size in one sentence. Then, state the group trend for anion size in one MORE sentence.

60. Determine the group trends for cation size
Determine the group trends for cation size. Then the group trend for anion size as well.
Group 1
Atoms/cations
Group 1 cation electron configurations
Li+1 2
Na+1
2-8
K+1
2-8-8
Rb+1
Group 17
Atoms/anions
Group 17 anion electron configurations
F-1
2-8
Cl-1
2-8-8
Br-1
I-1
71. The group trend for cation size is increasing The group trend for anion size is increasing.
72. WHY? Because going down any group (atom/ion) you always add orbitals.

61. 73. For METALS… How does each atom compare to it’s cation?
Cations are smaller than their atoms always, because they have less orbitals.
74. For NONMETALS… How does each atom compare to it’s anion?
Anions are always slightly larger than their atoms, because they have more electrons repelling each other in the same number of orbitals.

62. Cation Electron configuration
Period Trend for Cation size…
Cations:
Na+1
Mg+2
Al+3
Cation Electron configuration
2-8
These 3 metals in a row are all isoelectric to neon (have the same electron configuration).
Are they all going to be the same size? Is there something else, besides just the same electron configuration going on here? Think about the rest of the atom parts.
What’s going on in the nucleus?
75. State the Period Trend for Cation Size.

63. Cation Electron configuration
Period Trend for Cation size…
Cations:
Na+1
Mg+2
Al+3
Cation Electron configuration
total electrons
Number of protons
11p+
12p+
13p+
With more and more protons pulling the SAME NUMBER OF ELECTRONS, each cation will get smaller and smaller.
The period trend for cation size is decreasing.

64. Electron configuration
76. Fill in the chart… Period Trend for Anion size…
Anions:
N-3
O-2
F-1
Electron configuration
Number of protons
77. Write the period trend for anion size.

65. Electron configuration
Period Trend for Anion size…
Anions:
N-3
O-2
F-1
Electron configuration
total electrons
Number of protons
7p+
8p+
9p+
With more and more protons pulling the SAME NUMBER OF ELECTRONS, each anion will get smaller and smaller.
77. The period trend for anion size is decreasing.

66. Recap:
78. Cations are always lots smaller than their atoms, because the cations lose orbitals when they lose electrons.
79. Anions are always slightly larger than their atoms because the extra electrons stretch the orbital a bit as they repel from each other.
80. The group trend for cation size is increasing (because they add orbitals)
81. The group trend for anion size is increasing (because they add orbitals)

67. Recap:
82. The period trend for cation size is decreasing (because with the same number of electrons in the same number of orbitals, the additional protons in the nucleus pull the anions tighter and tighter together.)
83. The period trend for anion size is decreasing (because with the same number of electrons in the same number of orbitals, the additional protons in the nucleus pull the anions tighter and tighter together.)

68. Take out your homework 1-3 assignments Homework # 1
1. What is the definition of nuclear charge of an atom?
2. What are the net nuclear charges for these 10 atoms? Mg Sc V Cr Ir Au Hg Pb Al P
3. What is the GROUP TREND for net nuclear charge going down any group?
4. What is the PERIOD TREND for the net nuclear charge going across any period?
HOMEWORK # 2
1. List all atoms in Period 4. Show the atomic masses for each (use ACTUAL
VALUES on periodic table, DO NOT ROUND THESE.) Describe the PERIOD TREND for atomic masses.
2. Explain what happens with Cobalt and Nickel. Does this destroy the trend?
3. Explain why atoms get SMALLER going across periods.

69. You should hand in the Review Lab #2 now.
Forget the boxes for now, answer the questions:
1. Describe the GROUP TREND (going down a group) for Atomic Radius.
Describe the PERIOD TREND for Atomic Radius as you go ACROSS A PERIOD.
You should hand in the Review Lab #2 now.
You should also hand in the Boyle in a Bottle Lab now.
You should hand in these 3 HW’s now.
You should read the diary for Periodic Table Tonight
You should finish up the Review Lab #3 by Friday

70. Trends of the Periodic Table Class #5
Electronegativity

71. the idea that generated a Nobel Prize for Dr. Linus Pauling
Electronegativity
the idea that generated a Nobel Prize for Dr. Linus Pauling
This guy is the ONLY person ever to win 2 Nobel Prizes by himself. Some others shared two prizes, but, he’s really the man.

72. 84. Electronegativity is defined as the tendency to gain an electron in a bonding situation.
Bonding is a very complicated matter. There’s all kinds of bonds: covalent between 2 or more nonmetals, ionic bonds form between ions, metallic bonds form between atoms of metals that are stuck together, there are at least 3 kinds of intermolecular bonds, and some other odd ball ones too (resonance bonds, hybrid bonds, etc.)
Dr. Pauling measured how fairly two atoms could be expected to share electrons when bonding.
YOU ME

73. 87. When the EN difference is zero, the bond is NONPOLAR
2 identical atoms, like the HONClBrIF twins, will of course share their electrons perfectly, because as much as one hydrogen “wants” that electron from his partner, the desire to gain an electron in a bonding situation is equal for both.
85. Hydrogen has an electronegativity value of 2.2
86. No units! (finally!)
Each hydrogen in H2 has the same electronegativity value, so there is no electronegativity difference.
87. When the EN difference is zero, the bond is NONPOLAR
No difference means that each shares nicey-nice. (not like me and you and the cherry pie ala mode!)
Let’s look at HCl next.

74. Hydrogen and chlorine “fit” together in a 1:1 ratio
Hydrogen and chlorine “fit” together in a 1:1 ratio. Both the hydrogen and the chlorine “want” to fill up their orbitals by sharing electrons together as they covalently bond.
88. What are the EN values for H and Cl? Look at Table S
There’s a huge difference between them!
89. The greater the difference in electronegativity values, the more polar the bond The atom with the higher electronegativity value will “get” the electron in the bond more of the time.
91. That side of the bond will be more negative.
H-Cl
Difference is 1.0
In this case, chlorine will have a full third orbital most of the time, and hydrogen will have a full single orbital sometimes.

75. Group 1 electronegativity values Group 17 electronegativity values
92. What is the group trend for electronegativity value in group 2 and group 17?
Group 1
Atoms
Group 1 electronegativity values Li Na K Rb
Group 17
Atoms
Group 17 electronegativity values F Cl Br I
93. State the group trend for electronegativity values.

76. Group 1 electronegativity values Group 17 electronegativity values
What is the group trend for electronegativity value in group 2 and group 17?
Group 1
Atoms
Group 1 electronegativity values Li
1.0 Na
0.9 K
0.8 Rb
Group 17
Atoms
Group 17 electronegativity values F
4.0 Cl
3.2 Br
3.0 I
2.7
The group trend for electronegativity value is decreasing.
The reason for this is that electrons would be added into the outermost (valence) orbital, which is always further and further from the nucleus as you add orbitals going down a group. There is less pull inward.

77. Electro- negativity values
94. Indicate the Electronegativity Values.
Period 2 atoms Li Be B C N O F Ne
Electro- negativity values
95. State the period trend for electronegativity values, then
96. Explain neon’s electronegativity value???

78. Electro- negativity values
Determine the Period Trend for Electronegativity Values.
Period 2 atoms Li Be B C N O F Ne
Electro- negativity values
1.0
1.6
2.0
2.6
3.0
3.4
4.0
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The period trend for electronegativity is increasing.
As you go across the table, atoms become more likely to “take” an electron in a bonding situation.
Neon: Neon, and the noble gases do not make bonds, they don’t have electronegativity values…

79. Relative scales and arbitrary scales… (Dr
Relative scales and arbitrary scales… (Dr. Linus was a fun guy, and not a fungi)
97. A relative scale is one that compares all members of the group to one set standard.
98. Electronegativity is a relative scale, all atoms being relative to fluorine. Dr. Pauling determined that fluorine has the greatest tendency to gain electrons in a bonding situation.
99. An arbitrary scale is one that uses numbers that don’t really matter. Dr. Pauling choose 4.0 for his highest value, given only to fluorine. All other values ranged down to zero.
He could have use 100 as his top value, or eleven, or even He picked it for his own reason. There are not 4.0 somethings, in fact there is not even a unit here.
100. Electronegativity is both a relative scale, and it’s an arbitrary one as well.