Periodic Table

Trends & Definitions

How to read the Periodic Table

6

CCarbon

12.011

Atomic Number

Elemental Symbol

Elemental Name

Atomic Mass

Periodic Law

• When elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals.

0

50

100

150

200

250

0 5 10 15 20

Ato

mic

Ra

diu

s (p

m)

Atomic Number

Chemical Reactivity

• Families• Similar valence e- within a group result in similar

chemical properties

Periodic Trends are Influenced by:

• Energy Level• Higher energy levels are further from the nucleus

• Charge on Nucleus (# of protons)• More charge pulls the electrons in closer• + and – attract each other more

• Shielding Effect• Blocking effect

Periodic Trends• Atomic Radius

• size of atom: half the distance between two nuclei of a diatomic molecule

• Increases to the LEFT and DOWN

1

2

3

4 5

6

7

Atomic Radius

• Why larger going down?• Higher energy levels have larger orbitals

• Shielding - core e- block the attraction between the nucleus and the valence e-

• Why smaller to the right? • Increased nuclear charge without additional

shielding pulls e- in tighter

Periodic Trends

• First Ionization Energy• Energy required to remove one e- from a

neutral atom.• Increases going UP and to the RIGHT

1

2

3

4 5

6

7

Periodic Trends

• Melting/Boiling Point• Highest in the middle of a period.

1

2

3

4 5

6

7

Periodic Trends• Electronegativity

• Tendency of an atom to attract electrons when chemically combined

1

2

3

4 5

6

7

Ionic Radius

• Cations (+)• lose e-• smaller

• Anions (–)• gain e-• larger

© 2002 Prentice-Hall, Inc.

Ion Group trends

• Each step down a group is adding an energy level

• Ions therefore get bigger as you go down, because of the additional energy level.

Li1+

Na1+

K1+

Rb1+

Cs1+

Ion Period Trends• Across the period from left to right, the

nuclear charge increases - so they get smaller.

• Notice the energy level changes between anions and cations.

Li1+

Be2+

B3+

C4+

N3-O2- F1-

Size of Isoelectronic ions

• Iso- means “the same”• Isoelectronic ions have the same # of

electrons• Al3+ Mg2+ Na1+ Ne F1- O2- and N3-

• all have 10 electrons• all have the same configuration:

1s22s22p6 (which is the noble gas: neon)

Size of Isoelectronic ions?

• Positive ions that have more protons would be smaller (more protons would pull the same # of electrons in closer)

Al3+

Mg2+

Na1+ Ne F1- O2- N3-

13 12 11 10 9 8 7