1. Electron Configuration and the Periodic Table
Chemistry
Second Edition
Julia Burdge
Lecture PowerPoints
Jason A. Kautz
University of Nebraska-Lincoln 7
Electron Configuration and the Periodic Table 1
Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Electron Configuration and the Periodic Table7
7.1 Development of the Periodic Table
7.2 The Modern Periodic Table
Classification of Elements
Representing Free Elements in Chemical Equations
7.3 Effective Nuclear Charge
7.4 Periodic Trends in Properties of Elements
Atomic Radius
Ionization Energy
Electron Affinity
Metallic Character
7.5 Electron Configuration of Ions
Ions of Main Group Elements
Ions of d-Block Elements
7.6 Ionic Radius
Comparing Ionic Radius with Atomic Radius
Isoelectronic Series

3. Electron Configuration and the Periodic Table7
7.7 Periodic Trends in Chemical Properties of the Main Group Elements
General Trends in Chemical Properties
Properties of the Active Metals
Properties of Other Main Group Elements
Comparison of Group 1A and Group 1B Elements
Variation in Properties of Oxides Within a Period

4. Development of the Periodic Table
7.1
In 1864 John Newlands referred to the law of octaves.
In 1869 Dmitri Mendeleev and Lothar Meyer independently proposed the idea of periodicity.
Mendeleev grouped elements (66) according to properties.
Mendeleev predicted properties for elements not yet discovered.
Mendeleev could not explain inconsistencies.

5. Development of the Periodic Table
In 1913 Henry Moseley discovered the correlation between the number of protons (atomic number) and frequency of X-rays generated .
Entries today include atomic number and symbol; and are arranged according to electron configuration.

6. The Modern Periodic Table
7.2

7. The Modern Periodic Table
The main group elements (also called the representative elements) are the elements in Groups 1A through 7A.

8. The Modern Periodic Table
The noble gases are found in Group 8A.

9. The Modern Periodic Table
The transition metals are found in Group 1B and 3B through 8B.
Group 2B have filled d subshells and are not transition metals.

10. The Modern Periodic Table
The lanthanides and actinides make up the f-block elements.

11. The Modern Periodic Table
There is a distinct pattern to the electron configurations of the elements in a particular group.
For Group 1A: [noble gas]ns1
For Group 2A: [noble gas]ns2

12. The Modern Periodic Table
The outermost electrons of an atom are called the valence electrons.
Valence electrons are involved in the formation of chemical bonds.
Similarity of valence electron configurations help predict chemical properties.
For Group 1A: [noble gas]ns1
valence
core
For Group 2A: [noble gas]ns2
valence
core
For Group 7A: [noble gas]ns2np5
valence
core

13. The Modern Periodic Table
Metals are always represented by their empirical formulas.
Nonmetals may be written as an
empirical formula (C) or as polyatomic
molecules (H2, N2, O2, F2, Cl2, Br2, I2,
and P4).
Sulfur is usually written as S instead of S8
elemental sulfur (S)
elemental sodium (Na)

14. The Modern Periodic Table
Noble gases all exist as isolated atoms and are represented with their elemental symbol (Xe, He, etc.)
Metalloids are represented with empirical formulas (B, Si, Ge, etc.)
Neon(Ne)
Silicon (Si)

15. Effective Nuclear Charge
7.3
Effective Nuclear Charge (Zeff) is the actual magnitude of positive charge that is experienced by an electron in the atom.
Z is the nuclear charge or simply the number of protons in the nucleus.
σ is the shielding constant.
Zeff increases from left to right across a period; changes very little down a column
Zeff = Z – σ Li Be B C N O F Z 3 4 5 6 7 8 9
Zeff
1.28
1.91
2.42
3.14
3.83
4.45
5.10

16. Effective Nuclear Charge
Effective Nuclear Charge (Zeff) is the actual magnitude of positive charge that is experienced by an electron in the atom.
Zeff = Z – σ

17. Periodic Trends in Properties of Elements
7.4
Atomic radius is the distance between the nucleus of an atom and its valence shell.
The metallic radius is half the distance between the nuclei of two adjacent, identical metal atoms.

18. Periodic Trends in Properties of Elements
The covalent radius is half the distance between adjacent, identical nuclei in a molecule.

19. Periodic Trends in Properties of Elements
The atomic radius increases from top to bottom down a group.
~increasing n
Atomic radius decreases from left to right across a period.
~increasing Zeff

20. Periodic Trends in Properties of Elements
Atomic radius decreases left to right across a period due to increased electrostatic attraction between the effective nuclear charge and the charge on the valence shell.

21. Periodic Trends in Properties of Elements
Ionization energy (IE) is the minimum energy required to remove an electron from an atom in the gas phase.
IE1(Na) = kJ/mol.
Na(g) → Na+(g) + e−

22. Periodic Trends in Properties of Elements
IE1 value for the main group elements (kJ/mol).

23. Periodic Trends in Properties of Elements
First ionization energy as a function of atomic number.

24. Periodic Trends in Properties of Elements

25. Periodic Trends in Properties of Elements

26. Periodic Trends in Properties of Elements
It is possible to remove additional electrons in subsequent ionizations.
IE1(Na) = 496 kJ/mol.
IE2(Na) = 4562 kJ/mol.
Na(g) → Na+(g) + e−
Na+(g) → Na2+(g) + e−

27. Periodic Trends in Properties of Elements
It takes more energy to remove the 2nd, 3rd, 4th, etc. electrons and even much more energy to remove core electrons.
Core electrons are closer to nucleus
Core electrons experience greater Zeff

28. Periodic Trends in Properties of Elements
Electron Affinity (EA) is the energy released when an atom in the gas phase accepts an electron.
Cl(g) + e‒→ Cl‒(g)

29. Periodic Trends in Properties of Elements
Electron Affinity (EA) is the energy released when an atom in the gas phase accepts an electron.

30. Periodic Trends in Properties of Elements
It is easier to add an electron to an s orbital than to add one to a p orbital with the same principal quantum number.

31. Periodic Trends in Properties of Elements
Within a p subshell, it is easier to add an electron to an empty orbital than to add one to an orbital that already contains an electron.

32. Periodic Trends in Properties of Elements
More than one electron may be added to an atom.
Process
ΔH (kJ/mol)
Electron Affinity
O(g) + e− → O−(g)
−141
EA1 = 141 kJ/mol
O− (g) + e− → O2−(g)
744
EA2 = −741 kJ/mol
A significantly endothermic process happens only in concert with one or more exothermic processes

33. Periodic Trends in Properties of Elements
Metals tend to
Be shiny, lustrous and malleable
Be good conductors of heat and electricity
Have low ionization energies (form cations)
Form ionic compounds with chlorine (metal chlorides)
Form basic compounds with oxygen (metal oxides)

34. Periodic Trends in Properties of Elements
Nonmetals tend to
Vary in color and are not shiny
Be brittle, rather than malleable
Be poor conductors of electricity
Form acidic, molecular compounds with oxygen
Have high electron affinities (form anions)

35. Periodic Trends in Properties of Elements
Metalloids are elements with properties intermediate between those of metals and nonmetals.

36. Electron Configurations of Ions
7.5
To write the electron configuration of an ion formed by a main group element:
Write the configuration for the atom.
Add or remove the appropriate number of electrons.
Na: 1s22s22p63s1
Na+: 1s22s22p6
10 electrons total, isoelectronic with Ne
Cl: 1s22s22p63s23p5
Cl‒: 1s22s22p63s23p6
18 electrons total, isoelectronic with Ar

37. Electron Configurations of Ions
Ions of d-block elements are formed by removing electrons first from the shell with the highest value of n.
Fe: [Ar]4s23d 6
Fe2+: [Ar]3d 6
Fe: [Ar]4s23d 6
Fe3+: [Ar]3d 5

38. Ionic Radius
7.6
The ionic radius is the radius of a cation or an anion.
Cations are always smaller than their atoms.
Anions are always larger than their atoms.
The ionic radius affects physical and chemical properties of an ionic compound.

39. O2‒: 1s22s22p6 F‒: 1s22s22p6 Ne: 1s22s22p6 Ionic Radius
An isoelectronic series is a series of two or more species that have identical electron configurations but different nuclear charges.
O2‒: 1s22s22p6
F‒: 1s22s22p6
Ne: 1s22s22p6
isoelectronic

40. Periodic Trends in Chemical Properties of the Main Group Elements
7.7
IE and EA enable us to understand types of reactions that elements undergo and the types of compounds formed.

41. Periodic Trends in Chemical Properties of the Main Group Elements
Hydrogen (1s1)
Grouped by itself
Forms a cation with a +1 charge (H+)
Forms an anion with a ‒1 charge (H‒)
Hydrides react with water to produce hydrogen gas and a base.
CaH2(s) + H2O(l) → Ca(OH)2(aq) + H2(g)

42. Periodic Trends in Chemical Properties of the Main Group Elements
Group 1A elements (ns1, n ≥ 2)
Low IE
Never found in nature in pure elemental state
React with oxygen to form metal oxides

43. Periodic Trends in Chemical Properties of the Main Group Elements
Group 2A elements (ns2, n ≥ 2)
Less reactive than 1A
Some react with H2O to produce H2
Some react with acid to produce H2

44. Periodic Trends in Chemical Properties of the Main Group Elements
Group 3A elements (ns2np1, n ≥ 2)
Metalloid (B) and metals (all others)
Al forms Al2O3 with oxygen
Al forms +3 ions in acid
Others form +1 and +3

45. Periodic Trends in Chemical Properties of the Main Group Elements
Group 4A elements (ns2np2, n ≥ 2)
Nonmetal (C); metalloids (Si, Ge) and others metals
Form +2 and +4 oxidation states
Sn, Pb react with acid to produce H2

46. Periodic Trends in Chemical Properties of the Main Group Elements
Group 5A elements (ns2np3, n ≥ 2)
Nonmetal (N2, P) metalloid (As, Sb) and metal (Bi)
Nitrogen, N2 forms variety of oxides
Phosphorus, P4
As, Sb, Bi (crystalline)
HNO3 and H3PO4 important industrially

47. Periodic Trends in Chemical Properties of the Main Group Elements
Group 6A elements (ns2np4, n ≥ 2)
Nonmetals (O, S, Se)
Metalloids (Te, Po)
Oxygen, O2
Sulfur, S8
Selenium, Se8
Te, Po (crystalline)
SO2, SO3, H2S, H2SO4

48. Periodic Trends in Chemical Properties of the Main Group Elements
Group 7A elements (ns2np5, n ≥ 2)
All diatomic
Do not exist in elemental form in nature
Form ionic “salts”
Form molecular compounds with each other

49. Periodic Trends in Chemical Properties of the Main Group Elements
Group 8A elements (ns2np6, n ≥ 2)
All monatomic
Filled valence shells
Considered “inert” until 1963 when Xe and Kr were used to form compounds
No major commercial use

50. Periodic Trends in Chemical Properties of the Main Group Elements
Comparison of Group 1A and Group 1B Elements
Have single valence electron
Properties differ
Group 1B much less reactive than 1A
High IE of 1B - incomplete shielding of nucleus by inner “d” - outer “s” electron of 1B strongly attracted to nucleus
1B metals often found elemental in nature (coinage metals)

51. Periodic Trends in Chemical Properties of the Main Group Elements

52. Chapter Summary: Key Points7
Development of Periodic Table
The Modern Periodic Table
Classification of Elements
Free Elements in Chemical Equations
Effective Nuclear Charge
Periodic Trends in Properties of Elements
Atomic Radius
Ionization Energy
Electron Affinity
Metallic Character
Electron Configuration of Ions
Ions of Main Group Elements
Ions of d-Block Elements
Ionic Radius
Comparing Ionic Radius with Atomic Radius
Isoelectronic Series
Periodic Trends in Chemical Properties of the Main Group Elements
General Trends in Chemical Properties
Properties of the Active Metals
Properties of Other Main Group Elements
Comparison of Group 1A and Group 1B Elements
Variation in Properties of Oxides Within a Period