1. Section 5.3 Periodicity Trends
Objectives:
To state the trend in atomic size within a group or period of elements.
To state the trend in metallic character within a group or period.

2. PERIODICITY -based upon
-trend in properties of element across a “period” & within a “group”
-based upon
1) Effective Nuclear Charge (ENC) - ENC = # protons - # core (kernal / inner) electrons - aka: Coulombic Attraction attraction between (+) & (-) charges based upon 1) Amount of CHARGE ) Distance
Across the period, ENC INCREASES due increase # p+ & e-
Objectives:
To state the trend in atomic size within a group or period of elements.
To state the trend in metallic character within a group or period.

3. Coulombic Attraction opposites attract like repels 2) Distance
Based upon…..
1) Amount of Charge
opposites attract
like repels
2) Distance
between charges A 1+ 1- 2+ 2- B 2+ 2- C

4. + 2) Shielding Effect - - - - nucleus Electron Shield Valence
Across a period, ,
shielding effect
CONSTANT
Why?
SAME ENERGY LEVEL (distance)
Valence + -
nucleus - -
Within a group,
shielding effect
INCREASES
due to
INCREASE
ENERGY
LEVELS
(distance)
Electrons -
Electron Shield
“kernel” (Inner or Core) electrons
Kernel electrons block the attractive force of the nucleus from the valence electrons

5. Atomic Radius:the size of a NEUTRAL atom-
Across the period, atomic radius decreases because there is an increase in nuclear charge and Effective Nuclear Charge (# protons – # core electrons).
As the attraction between the (+) nucleus and the (–) valence electrons , the atomic size . Greater coulombic attraction.
Each valence electron is pulled by the full ENC
Within a group/family, atomic radius INCREASES Why? Increase SHIELDING Li Be B
1s22s1
1s22s2
1s22s22p1
(ENC = 1)
(ENC = 2)
(ENC = 3) Li Be B + + + + + + + + + + + +

6. Atomic Radii Within a group/family: atomic radius INCREASES because of INCREASE SHIELDING
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 175

7. Atomic Radius Example: Place the following elements in order from smallest to largest atomic radius & explain why? C, O, Sn, Sr
ANSWER: O < C < Sn < Sr O < C …Increase ENC with “O” C < Sn…Increase SHIELDING with “Sn” Sn < Sr…Increase ENC with “Sn” 7

8. Ionization Energy (IE): the energy required to remove an e– from an atom
Across the period, ionization energy INCREASES, due to increase ENC.
Within a group, ionization energy DECREASES, due to increase SHIELDING.
M + 1st I.E.
M e–
removes 1st e–
M nd I.E.
M e–
M rd I.E.
M e–
Each successive ionization requires more energy than the previous one
Why? Increase Positive Charge (stronger pull from the nucleus) 8

9. Ionization Energies (kJ/mol)
Element Na Mg Al Si P S Cl Ar
1st
498
736
577
787
1063
1000
1255
1519
2nd
4560
1445
1815
1575
1890
2260
2295
2665
3rd
6910
7730
2740
3220
2905
3375
3850
3945
4th
9540
10,600
11,600
4350
4950
4565
5160
5770
5th
13,400
13,600
15,000
16,100
6270
6950
6560
7320
6th
16,600
18,000
18,310
19,800
21,200
8490
9360
8780
Ionization energy increases with the removal of each additional electron.
Metals have low ionization energy; nonmetals have high ionization energy.
This experimental data gives evidence for:
1) effect of increasing nuclear charge
2) stability of octet
3) effect of increased radius
4) s & p sublevel in outer level
SUGGESTION: Emphasize that theories came from experimental evidence!
Herron, Frank, Sarquis, Sarquis, Cchrader, Kulka, Chemistry 1996, Heath, page
Shaded area on table denotes core electrons. 9

10. Ionization Energy Example: Place the following elements in order from smallest to largest 1st IE & explain why? Al, Ar, Cs, Na
ANSWER: Cs < Na < Al < Ar Cs < Na …Increase SHIELDING with “Cs” Na < Al …Increase ENC with “Al” Al < Ar…Increase ENC with “Ar” 10

11. First Ionization energyHe
Helium (He) has…
a greater IE than H
same shielding
greater nuclear charge n H
First Ionization energy He H 1+ 2+
1e-
2e-
Atomic number

12. First Ionization energyHe
Li has…
lower IE than H
more shielding
Further away outweighs greater nuclear charge n H
First Ionization energy Li
Atomic number

13. First Ionization energyHe
Helium (He) has…
a greater IE than H
same shielding
greater nuclear charge n H
First Ionization energy He H 1+ 2+
1e-
2e-
Atomic number

14. First Ionization energyHe
Li has…
lower IE than H
more shielding
Further away outweighs greater nuclear charge n H
First Ionization energy Li
Atomic number

15. First Ionization energyHe
Be has higher IE than Li
same shielding
greater nuclear charge n
1e-
2e- 3+ 4+ H 3+ 4+
2e-
1e-
First Ionization energy Be Be Li Li
Atomic number

16. First Ionization energyHe
B has lower IE than Be
same shielding
greater nuclear charge
p-orbitals available n
2e- 4+
3e- 5+ 4+ 5+
2e-
3e- H
First Ionization energy Be B Be B Li 2s 2p 1s
Atomic number

17. First Ionization energyHe n H
First Ionization energy C Be B Li 2s 2p 1s
Atomic number

18. First Ionization energyHe n N H
First Ionization energy C Be B Li 2s 2p 1s
Atomic number

19. First Ionization energyHe n N
Breaks the pattern because
removing an electron
gets to ½ filled p-orbital H O
First Ionization energy C Be B Li 2s 2p 1s
Atomic number

20. First Ionization energyHe n F N H O
First Ionization energy C Be B Li 2s 2p 1s
Atomic number

21. First Ionization energyHe Ne n F N
Ne has a lower IE than He
Both are full energy levels,
Ne has more shielding
Greater distance H O
First Ionization energy C Be B Li 2s 2p 1s
Atomic number

22. First Ionization energyH He Li Be B C N O F Ne Na n
Na has a lower IE than Li
Both are s1
Na has more shielding
Greater distance
First Ionization energy 2s 2p 1s 3s
Atomic number

23. Ionization Energy Example: Why does magnesium, phosphorus and zinc exhibit slightly higher ionization energies than the general trend within each of their period?
ANSWER: Irregularities occur with half filled & filled sublevels, because filled & half-filled sublevels are more stable. 23

24. Ionic Radius: the size of an ion ( + or – charged atom)
Metals
Nonmetals
Cations are smaller than parent atoms
Anions are larger than parent atoms Al
143 50 e
Group 13
Group 1
Group 17 e e
152
186
227 Li Na K 60
Li+ F-
136 F Cl Br 64 99
114 e e 95
Na+
Cl-
181
Al3+ e e
133 K+
Br-
195

25. The Octet Rule and Common Ions8+ - 9+
11+
12+
10+ -
Oxygen atom O
1s22s22p4
Fluorine atom F
1s22s22p5
Neon atom Ne
1s22s22p6
Sodium atom Na
1s22s22p63s1
Magnesium atom Mg
1s22s22p63s2
+2e-
+1e-
-1e-
-2e- 8+ - 9+ -
11+ -
12+ -
Oxygen ion
O2-
1s22s22p6
Fluorine ion
F1-
1s22s22p6
Sodium ion
Na1+
1s22s22p6
Magnesium ion
Mg2+
1s22s22p6

26. Isoelectronic Species
Isoelectronic – different element with the same number of electrons.
p = 8
n = 8
e = 10
p = 9
n = 9
e = 10
p = 10
n = 10
e = 10
p = 11
n = 11
e = 10
p = 12
n = 12
e = 10 8+ - 9+ -
10+ -
11+ -
12+ -
Oxygen ion
O2-
1s22s22p6
Fluorine ion
F1-
1s22s22p6
Neon atom Ne
1s22s22p6
Sodium ion
Na1+
1s22s22p6
Magnesium ion
Mg2+
1s22s22p6
Can you come up with another isoelectronic series of five elements?

27. Oxidation Number: most common ION it will form1 8
Groups 2
Li1+
Be2+
F1-
O2-
Cl1-
Na1+
Mg2+
Al3+
S2-
Br1-
K1+
Ca2+
Zn2+
Ga3+
Se2-
I1-
Rb1+
Sr2+
Ag1+
In3+
Te2-
Many elements have a tendency to gain or lose enough electrons to attain the same number of electrons as the noble gas closest to them in the periodic table.
Monatomic ions contain only a single atom.
Charges of most monatomic ions derived from the main group elements are predicted by simply looking at the periodic table and counting how many columns an element lies from the extreme left or right.
Transition metals form cations
with various charges.
Cs1+
Ba2+
Group 1: 1+ Group 16: 2-
Group 2: Group 17: 1- 27

28. Stop

29. What is “PERIODICITY”?
Periodicity is predictable repeating patterns/trends on the periodic table.
Objectives:
To state the trend in atomic size within a group or period of elements.
To state the trend in metallic character within a group or period. 29

30. What is “PERIODICITY” based upon?
1) EFFECTIVE NUCLEAR CHARGE ENC = # protons - # core (kernal / inner) electrons attraction between (+) & (-) charges deals with ) Amount of CHARGE ) DISTANCE between charges
- Across the period, ENC INCREASES due increase # p+ & e-
2) SHIELDING EFFECT Kernel (core / inner) electrons block the attractive force of the nucleus from the valence electrons
- Across a period, shielding effect CONSTANT Why? SAME ENERGY LEVEL (distance)
- Within a group, shielding effect INCREASES Due to INCREASE ENERGY LEVELS (distance)
Objectives:
To state the trend in atomic size within a group or period of elements.
To state the trend in metallic character within a group or period. 30

31. 1st Ionization Energies (KJ/mol)
Why are their “dips” in the 1st IE for Be and N?
Irregularities occur with filled & half-filled sublevels because they are more stable.

32. Why is there are huge jump between the 2nd IE & the 3rd IE for Mg?
2nd IE = Mg+2 which looks like the noble gas [Ne] It take a lot of energy to break a noble gas configuration.

33. Electronegativity
A measure ability of an atom in a chemical compound to attract electrons
Across a period, EN’s INCREASE WHY? Increase Nuclear Charge
Within a group/family, EN’s DECREASE or remain the same WHY? Increase Shielding

34. Electronegativities Period H B P As Se Ru Rh Pd Te Os Ir Pt Au Po At
2.1 B
2.0 P As Se
2.4 Ru
2.2 Rh Pd Te Os Ir Pt Au Po At 1 1 2A 3A 4A 5A 6A 7A
Actinides: Li
1.0 Ca Sc
1.3 Sr Y
1.2 Zr
1.4 Hf Mg La
1.1 Ac
Lanthanides: * y Be
1.5 Al Si
1.8 Ti V
1.6 Cr Mn Fe Co Ni Cu
1.9 Zn
1.7 Ga Ge Nb Mo Tc Ag Cd In Sn Sb Ta W Re Hg Tl Pb Bi C
2.5 S Br
2.8 I N
3.0 O
3.5 F
4.0 Cl 2 2 Na
0.9 K
0.8 Rb Cs
0.7 Ba Fr Ra
Below 1.0 3 3 3B 4B 5B 6B 7B 8B 1B 2B
Period 4 4 5 5 6 6
Linus Pauling ( ) awarded Nobel Prize in chemistry in 1954 for his 1939 text, The Nature of the Chemical Bond,
and also won the Nobel Peace Prize in 1962 for his fight to control nuclear weapons.
The greater the electronegativity of an atom in a molecule, the more strongly it attracts the electrons in a covalent bond. 7

35. Across a period, electron affinity INCREASES
Electron Affinity - the energy change associated with the addition of an electron
Across a period, electron affinity INCREASES
WHY? Increase Effective Nuclear Charge (ENC) with Constant Shielding
Within a group/family, electron affinity DECREASES
WHY? Increase SHIELDING effect (Slight Increase ENC – but Shielding predominates)
NOTE: BACKWARD SCALE SMALL NEGATIVE # LARGE NEGATIVE #
NOTE:Irregularities due to repulsive forces in the relatively small p orbitals.

36. Table of Electron Affinities

37. Summary of Periodic Trends
Shielding is constant
Atomic radius decreases
Ionization energy increases
Electronegativity increases
Nuclear charge increases 1A
Ionization energy decreases
Electronegativity decreases
Nuclear charge increases
Atomic radius increases
Shielding increases
Ionic size increases 2A 3A 4A 5A 6A 7A
Ionic size (cations) Ionic size (anions)
decreases decreases

39. Melting Points H He Mg Symbol Melting point oC Li Be B C N O F Ne
-259.2 He
-269.7 1 1 Mg
650
Symbol
Melting point oC Li
180.5 Be
1283 B
2027 C
4100 N
-210.1 O
-218.8 F
-219.6 Ne
-248.6 2 2
> 3000 oC oC Na 98 Mg
650 Al
660 Si
1423 P
44.2 S
119 Cl
-101 Ar
-189.6 3 3 K
63.2 Ca
850 Sc
1423 Ti
1677 V
1917 Cr
1900 Mn
1244 Fe
1539 Co
1495 Ni
1455 Cu
1083 Zn
420 Ga
29.78 Ge
960 As
817 Se
217.4 Br
-7.2 Kr
-157.2 4 4 Rb
38.8 Sr
770 Y
1500 Zr
1852 Nb
2487 Mo
2610 Tc
2127 Ru
2427 Rh
1966 Pd
1550 Ag
961 Cd
321 In
156.2 Sn
231.9 Sb
630.5 Te
450 I
113.6 Xe
-111.9 5 5 Cs
28.6 Ba
710 La
920 Hf
2222 Ta
2997 W
3380 Re
3180 Os
2727 Ir
2454 Pt
1769 Au
1063 Hg
-38.9 Tl
303.6 Pb
327.4 Bi
271.3 Po
254 At Rn
-71 6 6
Ralph A. Burns, Fundamentals of Chemistry , 1999, page 1999

40. Densities of Elements H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K
0.071 He
0.126 1 1 Li
0.53 Be
1.8 B
2.5 C
2.26 N
0.81 O
1.14 F
1.11 Ne
1.204 2 2 Na
0.97 Mg
1.74 Al
2.70 Si
2.4 P
1.82w S
2.07 Cl
1.557 Ar
1.402 3 3 K
0.86 Ca
1.55 Sc
(2.5) Ti
4.5 V
5.96 Cr
7.1 Mn
7.4 Fe
7.86 Co
8.9 Ni
8.90 Cu
8.92 Zn
7.14 Ga
5.91 Ge
5.36 As
5,7 Se
4.7 Br
3.119 Kr
2.6 4 4 Rb
1.53 Sr
2.6 Y
5.51 Zr
6.4 Nb
8.4 Mo
10.2 Tc
11.5 Ru
12.5 Rh
12.5 Pd
12.0 Ag
10.5 Cd
8.6 In
7.3 Sn
7.3 Sb
6.7 Te
6.1 I
4.93 Xe
3.06 5 5 Cs
1.90 Ba
3.5 La
6.7 Hf
13.1 Ta
16.6 W
19.3 Re
21.4 Os
22.48 Ir
22.4 Pt
21.45 Au
19.3 Hg
13.55 Tl
11.85 Pb
11.34 Bi
9.8 Po
9.4 At
--- Rn
4.4 6 6
Element Year Discovered Density (g/cm3)
Osmium
Iridium
Platinum
Rhenium
Neptunium
Plutonium
Gold prehistoric
Tungsten
Uranium
Tantalum
8.0 – 11.9 g/cm3
12.0 – 17.9 g/cm3
> 18.0 g/cm3 Mg
1.74
Symbol
Density in g/cm3C, for gases, in g/L W