1. Chapter 7 Periodic Properties of the Elements
Chemistry, The Central Science, 10th edition
Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Chapter 7 Periodic Properties of the Elements
John D. Bookstaver
St. Charles Community College
St. Peters, MO
 2006, Prentice Hall, Inc.

2. Development of Periodic Table
Elements in the same group generally have similar chemical properties.
Properties are not identical, however.

3. Effective Nuclear Charge
In a many-electron atom, electrons are both attracted to the nucleus and repelled by other electrons.
The nuclear charge that an electron experiences depends on both factors.

4. Shielding effect
Inner electrons “shield” the force of the nucleus on outer valence electrons
Force of the nucleus decreases on valence electrons, as the number of energy levels increases
Inner electrons repel outer energy levels of electrons
Follows Coulomb’s Law
Explains
Size of atoms
Energy required to remove a valence electron

5. Effective Nuclear Charge
Increases across a period
Increase in number of protons, increases nuclear force
Decreases down a group
Increase in energy levels, increases distance and therefore decreases force by nucleus

6. Sizes of Atoms atomic radius tends to…
…decrease from left to right across a period
due to increasing effective nuclear charge (more protons means greater force due to Coulomb’s Law pulling electrons closer)
…increase from top to bottom of a group
due to increasing number of energy levels

7. Sizes of Ions Ionic size depends upon: Nuclear charge.
Coulomb’s Law
Number of electrons.
Orbitals in which electrons reside.
Energy level in which electrons reside

8. Sizes of Ions Cations are smaller than their parent atoms.
The outermost electron is removed and repulsions are reduced.
Last electron is now in a lower energy level closer to the nucleus

9. Sizes of Ions Anions are larger than their parent atoms.
Electrons are added and repulsions are increased.
Since same effective nuclear charge but more electrons, electrons cannot be drawn as close making the ions larger

10. Sizes of Ions Ions increase in size as you go down a column.
Due to increasing number of energy levels

11. Sizes of Ions
In an isoelectronic series (period), ions have the same number of electrons.
Ionic size decreases with an increasing nuclear charge.

12. Ionization Energy
Amount of energy required to remove an electron from the ground state of a gaseous atom or ion.
First ionization energy is that energy required to remove first electron.

13. Trends in First Ionization Energies
As one goes down a column, less energy is required to remove the first electron.
the valence electrons are farther from the nucleus decreasing the nuclear force

14. Trends in First Ionization Energies
Generally, as one goes across a period, it gets harder to remove an electron.
As you go from left to right, effective nuclear charge increases making it more difficult to pull away an electron.

15. Electronegativity
Measure of the ability to attract and share electrons
(force between nucleus and valence electrons)
Increases across a period
Decreases down a group
Noble gases have no electronegativity they do not share electrons

16. Properties of Metal, Nonmetals, and Metalloids

17. Metals versus Nonmetals
Differences between metals and nonmetals tend to revolve around these properties.

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

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