1. Unit 8: Periodic Properties of the Elements
CHM 1045: General Chemistry and Qualitative Analysis
Unit 8: Periodic Properties of the Elements
Dr. Jorge L. Alonso
Miami-Dade College – Kendall Campus
Miami, FL
Textbook Reference:
Chapter #6
Module #10

2. Development of Periodic Table
Dmitry Ivanovich Mendeleyev ( ) noticed a repeating pattern of properties and reactivities, when the elements are ordered by increasing atomic numbers.

3. Development of Periodic Table

4. Development of Periodic Table
Phy.
Prop. Ca Sc Ti
At. # 20 21 22
Mass #
40.078
44.956
47.88
m.pt.
1112
1814
1933
b.pt.
1757
3104
3560
Density
1.55
2.99
4.54
Mendeleyev predicted the discovery and properties of Sc, Ga, Ge

5. Development of Periodic Table*

6. Periodic Trends
{Intro.Per.Prop*}
Size of atoms and ions: Determined by electrons which are both attracted to the nucleus and repelled by other electrons.
Ionization energy: energy required to remove an electron from and atom or ion. (Measure of how strongly an atom holds its own electrons)
Electron affinity: energy released when an atoms accept electrons. (Measure of how strongly an atom wants other electrons)
Metal, Non-metals, Metalloids
Group Trends: reactive characteristics determined by valence electrons.

7. Effective Nuclear Charge (Zeff )
Felt by
Shielding electrons (S)
Effective Nuclear Charge (Zeff)
Atomic Number (Z = #p+)
Zeff = Z S
Inner Core of Shielding e- = screening constant
Attractive Charge felt by valence electrons
Atomic Number (#p+)
{Eff.Nuclear.Charge*}

8. Effective Nuclear Charge (Zeff )
depends on both the fact that valence electrons are both:
attracted to the nucleus
repelled by the other (shielding) electrons.
Effective Nuclear Charge (Zeff.)
Increasing +1
Shielding electrons +8
(0e-) +2 +2 +3 +4 +5 +6 +7
(2e-)
(10e-)
(18e-)
(19e-) (20e-) (21e-) (22e-) (23e-) (24e-) (25e-) (26e-) (27e-) ( 28e-)

9. (1) Sizes of Atoms (Atomic Radii)
Bonding atomic radius tends to…
…decrease from left to right across a row due to increasing Zeff.
…increase from top to bottom of a column due to increasing value of n
increasing value of n
increasing Zeff.
{AtomicRadii*}

10. Sizes of Atoms (Atomic Radii)

15. Sizes of Atoms and Ions Experimental Techniques for determining radii:
X-ray crystallography
Neutron scattering

16. Sizes of Atoms
The bonding atomic radius is defined as one-half of the distance between covalently bonded nuclei.

17. Sizes of Ions {Grey = atom, Blue = anion} {Pink = cation, Grey = atom}
{SizeOfIons*}
Cations are smaller than their parent atoms.
The outermost electron is removed and repulsions are reduced.
Anions: larger than parent atoms.
Electrons are added and repulsions are increased.
{Grey = atom, Blue = anion}
{Pink = cation, Grey = atom}

18. Sizes of Ions Ions increase in size as you go down a column.
{Pink = cation, Grey = atom , Blue = anion}
Ions increase in size as you go down a column.
Due to increasing value of n.
Cations larger
Anions larger

19. Sizes of Ions
In an isoelectronic series, ions have the same number of electrons.
Ionic size decreases with an increasing nuclear charge.
{Pink = cation, Grey = atom , Blue = anion}

20. (2) Ionization Energy
the amount of energy required to remove an electron from the ground state of a gaseous atom or ion.
A good measure of how strongly metal ions hold-on to their electrons as they become cations: M  M+ + e-
Electron gun

21. Ionization Energy
{IonizationEnergy}
First ionization energy is that energy required to remove first electron.
Second ionization energy is that energy required to remove second electron, etc.
It requires more energy to remove each successive electron.
When all valence electrons have been removed, the ionization energy takes a quantum leap (large jump).

22. Trends in First Ionization Energies
As one goes up in a column, more energy is required to remove the first electron.
Zeff is essentially the same, but the valence electrons are closer to the nucleus. +1 +8
Zeff +2 +5 +3 +4 +6 +7

23. Trends in First Ionization Energies
As one goes across a row, the Zeff increases, so more energy is required to remove the first electron.
Zeff increases, but the valence electrons essentially in the same distance (energy level) from the nucleus. +1 +8
Zeff +2 +5 +7 +4 +6 +3

24. Trends in First Ionization Energies
Generally, across a row, the Zeff increases.
{IonizationEnergy}

25. Trends in First Ionization Energies
there are two apparent discontinuities in this trend.

26. Trends in First Ionization Energies
The first occurs between Groups IIA and IIIA.
Electron removed from p-orbital rather than s-orbital
Electron farther from nucleus
Small amount of repulsion by s electrons.

27. Trends in First Ionization Energies
The second occurs between Groups VA and VIA.
Electron removed comes from doubly occupied orbital.
Repulsion from other electron in orbital helps in its removal.

28. (3) Electron Affinity
Energy change accompanying addition of electron to gaseous atom:
Cl + e−  Cl−
A good measure of how strongly non-metal atom acquire electrons to become anions:
N + e-  N-
{ElectronAffinity}

29. Trends in Electron Affinity
In general, electron affinity becomes more exothermic as you go from left to right across a row.
{PerTrendElectAffinity}

30. Trends in Electron Affinity
There are again, however, two discontinuities in this trend.

31. Trends in Electron Affinity
The first occurs between Groups IA and IIA.
Added electron must go in p-orbital, not s-orbital.
Electron is farther from nucleus and feels repulsion from s-electrons.

32. Trends in Electron Affinity
The second occurs between Groups IVA and VA.
Group VA has no empty orbitals.
Extra electron must go into occupied orbital, creating repulsion.

33. (4) Properties of Metal, Nonmetals, and Metalloids

34. Metals versus Nonmetals
Metals tend to form cations.
Nonmetals tend to form anions.

35. Metals vs. Nonmetals Metals tend to be: lustrous Malleable and ductile
Good conductors of heat and electricity.
Loose electrons (cations) in reactions with nonmetals in order to acquire noble gas configuration
Unreactive with each, instead they mix with each other to form alloys (solutions)
Nonmetals tend to be:
Dull
Brittle
Poor conductors of heat and electricity.
Gain electrons (anions) in reactions with metals in order to acquire noble gas configuration.
Reactive with each other to form molecular (covalent) compounds.

36. Metals do not react with each other to form compounds, instead they mix with each other to form alloys (solutions)
Gold Gold Jewelry k =100% Au; 12k =50% Au, usually mixed with Ag, Pd or Ni (white) or Cu (rose); colored alloys coated with Rh or Pt to prevent rusting.
12k = 50%    mixed with Ag, Pd
24k =100% Au
mixed with Cu
mixed with Ni
{coated with Rh or Pt to prevent rusting}

37. Metal oxides vs. Nonmetal oxides
Nonmetal oxides tend to be acidic.
SO2 + H2O 
SO3 + H2O 
H2SO3(aq) weak acid
H2SO4(aq) strong acid
Note that the more oxidized the oxide the stronger its acid base strength!
CO2(s)
MgO
Na2O
CO2
SO3
Amphoteric: capable of behaving as an acid or a base.
Acid
H2O +
bromthymol
blue
Indicator
Basic
H2O +
bromthymol
blue
Indicator
Metal oxides tend to be basic.
CaO + HOH 
Ca2+ + 2OH-
CO2(s) + H2O(l)  H2CO3(aq) weak acid
H2CO3(aq)  CO2(g) + H2O(l)
{Acid/Base behavior of Oxides}

38. Metalloids Have some characteristics of metals, some of nonmetals.
For instance, silicon looks shiny, but is brittle and fairly poor conductor.

39. Not a Metalloid: Silicone
An organic compound made primarily from silicon and oxygen
Silicone overdose

41. (5) Group Trends Alkali Metals Nobel Gases Alkaline Earth Metals
Halogens

42. Alkali Metals Soft, metallic solids.
Name comes from Arabic word for ashes.
So reactive, that they are found only as compounds in nature.
Have low densities and melting points.
Also have low ionization energies.

43. Alkali Metals
Their reactions with water are famously exothermic.

44. . Alkali Metals Alkali metals react with oxygen to form oxides (O2-)
4K + O2  2K2O
Alkali metals (except Li) react with oxygen to form peroxides (O22-)
2K + O2  K2O2
K, Rb, and Cs also form superoxides (O2-):
K + O2  KO2
Produce bright colors when placed in flame. . 2
{ox # = -1}
{ox # = -½}

45. Alkaline Earth Metals
Have higher densities and melting points than alkali metals.
Have low ionization energies, but not as low as alkali metals.

46. Group 4A: The Carbon Family
Allotropes of Carbon:
a) Diamond
b) Graphite
c) Lonsdaleite
d) C60 (Buckminsterfullerene)
e) C540 (see Fullerene)
f) C70 (see Fullerene)
g) Amorphous carbon
h) single-walled carbon nanotube

47. Group 6A: The Oxygen Family
sulfur, and
selenium are nonmetals.
Tellurium is a metalloid.
The radioactive polonium is a metal.

48. Oxygen Sulfur Weaker oxidizing agent than oxygen.
Two allotropes: O2
O3, ozone
Oxidizing agent: Tends to take electrons from other elements
Three anions:
O2−, oxide
O22−, peroxide
O21−, superoxide
Sulfur
Weaker oxidizing agent than oxygen.
Most stable allotrope is S8, a ringed molecule.

49. Group VIIA: Halogens Prototypical nonmetals
Name comes from the Greek halos and gennao: “salt formers”
{PhyPropHalogens}

50. Group VIIA: Halogens Large, negative electron affinities
Therefore, tend to oxidize other elements easily
React directly with metals to form metal halides
Chlorine added to water supplies to serve as disinfectant

51. Group VIIIA: Noble Gases
Astronomical ionization energies
Positive electron affinities
Therefore, relatively unreactive
Monatomic gases

52. Group VIIIA: Noble Gases
Xe forms three compounds:
XeF2
XeF4 (at right)
XeF6
Kr forms only one stable compound:
KrF2
The unstable HArF was synthesized in 2000.

53. Metals versus Nonmetals

54. 2006 (B)

56. 2006 (A)

58. 2007 (B)