Transcript III. Periodic Trends

The Periodic Table
Atomic Radius (pm)
250
I. Periodic
Trends
200
150
100
50
0
0
5
10
Atomic Number
15
20
I
II
III
A. Chemical Reactivity
Families
Similar valence e- within a group result
in similar chemical properties
1
2
3
4
5
6
7
A. Chemical Reactivity
1
2
3
4
5
6
7
Alkali Metals
Alkaline Earth Metals
Transition Metals
Halogens
Noble Gases
B. Other Properties
Atomic Radius
size of atom
© 1998 LOGAL
© 1998 LOGAL
C. Atomic Radius
Atomic Radius
K
Atomic Radius (pm)
250
Na
200
Li
150
100
Ar
Ne
50
0
0
5
10
Atomic Number
15
20
C. Atomic Radius
Atomic Radius
Increases going DOWN a group
Why? Increased number of energy levels
1
2
3
4
5
6
7
C. Atomic Radius
Decreases moving from left to right
across a period.
Why? Increased effective nuclear
charge
Greater attraction between valence
electrons and protons in the nucleus
As you move across a
period, the number of valence
electrons and the number of
protons increases
Therefore, there is a
stronger attraction!
1
2
3
4
5
6
7
D. Ionization Energy
First Ionization Energy
Energy required to remove one e- from
an atom.
H(g) → H+(g) + e-
∆Ho = -1312.0 kJ/mol
He(g) → He+(g) + e-
∆Ho = 2372.3 kJ/mol
Li(g) → Li+(g) + e-
∆Ho = 572.3 kJ/mol
D. Ionization Energy
1st Ionization Energy (kJ)
First Ionization Energy
He
2500
Ne
2000
Ar
1500
1000
500
Li
Na
K
0
0
5
10
Atomic Number
15
20
E. Ionization Energy
First Ionization Energy
Increases UP and to the RIGHT
Why? Moving up a column there is a
stronger attraction between the electrons
and the nucleus
Moving across a period, there is also
increased attraction between the electrons
and the nucleus because decreased atomic
size
1
2
3
4
5
6
7
D. Ionization Energy
Successive Ionization Energies
Large jump in I.E. occurs when a CORE
e- is removed.
Mg
Core e-
1st I.E.
736 kJ
2nd I.E.
1,445 kJ
3rd I.E.
7,730 kJ
E. Ionic Radius
Ionic Radius
Cations (+)
lose esmaller
Anions (–)
gain e-
larger
© 2002 Prentice-Hall, Inc.
F. Electronegativity
*The measure of how strongly an atom attracts
another atom’s electrons
• Increases from left to right (except for noble
gases)
• Increases as you move up a group
1
2
3
4
5
6
7
Examples
Which atom has the larger radius?
Be or Ba
Ba
Ca or Br
Ca
Examples
Which atom has the higher 1st I.E.?
N or Bi
N
Ba or Ne
Ne
Examples
Which particle has the larger radius?
S or
2S
2S
Al or
3+
Al
Al