I

II

III

Periodic Trends

Valence Electrons

Electrons available to be lost, gained, or shared in the

formation of chemical compounds

Outer energy level

Atomic Radius

Distance from the center of atom’s nucleus to outermost electron.

1

2

3

4 5

6

7

Decreases UP and to the RIGHT Or Increases DOWN and to the LEFT

Atomic Radius

0

50

100

150

200

250

0 5 10 15 20Atomic Number

Ato

mic

Ra

diu

s (

pm

)Atomic Radius

Li

ArNe

KNa

Describe in terms of atomic structure:

Going down a group from top to bottom, adding energy levels.

Higher energy levels have larger orbital's

Describe in terms of atomic forces:

Shielding Effect ~ inner core e- block the attraction between the nucleus and the valence e-

Atomic Radius

Describe in terms of atomic structure: Electrons remain in the same energy level (not

farther away)

Describe in terms of atomic forces:

Increased nuclear charge (+) without additional shielding pulls e- in tighter

Atomic Radius

An atom or group of bonded atoms that has a positive or negative charge.

Ion

Cations (+)

lose e-

smaller

© 2002 Prentice-Hall, Inc.

Anions (–)

gain e-

larger

Ionic Radius

Larger – down a group.

Smaller – across a period.

Cations: Smaller than neutral atom

Anions: Larger than neutral atom

Ionic Radius

Trends in Ionic Size

Trends in Ionic Size

6.3S

ize

ge

ner

ally

incr

ease

s

1

2

3

4 5

6

7

The amount of energy required to remove an electron from a neutral atom.

Increases UP and to the RIGHT

Ionization Energy

Ionization Energy

Opposite trend from atomic radius. Larger atoms ~electrons held less

strongly ~ takes less energy to remove one.

Smaller atoms ~ electrons held more strongly ~ takes more energy to remove one.

Ionization Energy

Why small jumps within each group?

Ionization Energy

0

500

1000

1500

2000

2500

0 5 10 15 20Atomic Number

1st

Ion

izat

ion

En

erg

y (k

J)

Stable electron configurationsdo not easily give up electrons

Amount of energy to remove 1st electron, 2nd electron, 3rd electron.

Each higher ionization requires more energy.

Na Na+ + e- 496 KJ/mol

Na+ Na+2 + e- 4565 KJ/mol

Na+2 Na+3 + e- 6912 KJ/mol

*1st, 2nd, and 3rd Ionization Energies

Electron Affinity

The energy change that occurs when an electron is added to an atom.

Negative Electron Affinities

Energy is given off when an electron is added to an atom.

Non-Metals tend to gain electrons.

Non-Metals have NEGATIVE affinities.

Positive Electron Affinities

Energy is required to add an electron to an atom.

Metals tend to lose electrons

Metals have POSITIVE affinities.

Noble Gas Electron Affinities

Noble Gases have high positive electron affinities.

Octet Rule!

8 valence electrons

Electronegativity

The ability of an atom to attract electrons

Predict using octet rule and atomic radius.

F is most electronegative, Cs and Fr are least

electronegative.

Electronegativity