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Chapter 8

Periodic Properties of the Elements

Objectives

Periodic Trends in Properties of Elements• Electron Affinity• Metallic Characteristics

Electron Configuration of Ions• Ions of Main Group Elements• Ions of d-Block Elements

Ionic Radius• Comparing Ionic Radius with Atomic Radius• Isoelectronic Series

Electron Affinity

Electron affinity (EA) :

Why is the energy negative?

Why is it important to remember stability of an atom?

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Electron Affinity

Which atom is most likely to accept an electron? Why?-Define isoelectronic:

Electron Affinity (2)

How does electron affinity change across a periodic table?

Ionic Radius

The ionic radius is the radius of a cation or an anion.

Cations:

-what happens to effectivenuclear charge? Whathappens to the radius andwhy?

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Ionic Radius

The ionic radius is the radius of a cation or an anion.

Anions:

-what happens to effectivenuclear charge and why? What happens to the radiusand why?

Notes

Metallic Character

Metals tend toØ Be shiny, lustrous, malleable, and ductile

Ø Be good conductors of both heat and electricity

Ø Have low ionization energies (commonly form cations)

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Metallic Character (2)Nonmetals tend toØ Vary in color and are not shiny

Ø Be brittle, rather than malleable

Ø Be poor conductors of both heat and electricity

ØHave high electron affinities (commonly form anions)

Metallic Character (3)

Metalloids are elements with properties intermediate between those of metals and nonmetals.

Electron Configurations of Ions

To write the electron configuration of an ion formed by a main group element:

1) Write the configuration for the atom.

2) 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

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Ions of d-Block Elements

Ions of d-block elements are formed by removing electrons first from the shell with the highest value of n.

For Fe to form Fe2+, two electrons are lost from the 4s subshell not the 3d.

Fe: [Ar]4s23d 6 à Fe2+: [Ar]3d 6

Fe can also form Fe3+, in which case the third electron is removed from the 3d subshell.

Fe: [Ar]4s23d 6 à Fe3+: [Ar]3d 5

Objectives

Periodic Trends in Properties of Elements• Electron Affinity• Metallic Characteristics

Electron Configuration of Ions• Ions of Main Group Elements• Ions of d-Block Elements

Ionic Radius• Comparing Ionic Radius with Atomic Radius• Isoelectronic Series