Transcript Periodic table intro and trends

The Periodic Table
Atomic Radius (pm)
250
Periodic
Trends
200
150
100
50
0
0
5
10
Atomic Number
15
20
I
II
III
Periodic Properties
1. Atomic Radius
 ½ the distance between
two identical atoms
bonded together
2. Ionization Energy
© 1998 LOGAL
 Energy required to
remove one e- from a
neutral atom.
© 1998 LOGAL
Periodic Properties
3. Electron Affinity
 Attraction for additional electrons
4. Electronegativity
 “Pull” an atom has on
electrons when
bonded to another
atom
A. Atomic Radius
Atomic Radius
1. Increases to the LEFT and DOWN
1
2
3
4
5
6
7
A. Atomic Radius
2. Why larger going down?
a) Adding energy levels
b) Shielding - core e- block the attraction
between the nucleus and the valence e-
A. Atomic Radius
3. Why smaller to the right?
a) Increased nuclear charge (i.e. more
protons in nucleus) without more shielding
pulls e- in tighter
A. Atomic Radius
Na
11 p+
Cl
17 p+
Nucleus not strong enough to pull
Stronger nucleus pulls
valence e- in tight
valence e- in tight
B. Ionic Radius
Ionic Radius
Cations (+)
lose esmaller
Anions (–)
gain e-
larger
© 2002 Prentice-Hall, Inc.
B. Ionic Radius
Ionic Radius
“Tug of War” between positive
nucleus and negative electrons.
Cations: nucleus is “stronger”
Anions: electrons are “stronger”
Examples
Which atom has the larger radius?
Be or Ba
Ba
Ca or Br
Ca
Examples
Which particle has the larger radius?
S or
2S
2S
Al or
3+
Al
Al
C. Ionization Energy
First Ionization Energy – energy needed
to remove ONE electron.
1st Ionization Energy (kJ)
2500
He
Ne
2000
Ar
1500
1000
500
Li
Na
K
0
0
5
10
Atomic Number
15
20
C. Ionization Energy
First Ionization Energy
1. Increases UP and to the RIGHT
1
2
3
4
5
6
7
C. Ionization Energy
2. Why opposite of atomic radius?
a) In small atoms, e- are close to the
nucleus where the attraction is stronger;
it takes a lot of energy to strip an eaway!
3. Why small jumps within each group?
a) Stable e- configurations don’t want to
lose e-
C. Ionization Energy
4. Successive Ionization Energies
a) Large jump in I.E. occurs when a
CORE e- is removed after all
valence e- have been removed.
Mg
Core e-
1st I.E.
736 kJ
2nd I.E.
1,445 kJ
3rd I.E.
7,730 kJ
C. Ionization Energy
4. Successive Ionization Energies
a) Large jump in I.E. occurs when a
CORE e- is removed after all
valence e- have been removed.
Al
1st I.E.
577 kJ
Core e-
2nd I.E.
1,815 kJ
3rd I.E.
2,740 kJ
4th I.E.
11,600 kJ
Examples
Which atom has the higher 1st I.E.?
N or Bi
N
Ba or Ne
Ne
D. Electron Affinity
Electron Affinity
1. Increases UP and to the RIGHT
1
2
3
4
5
6
7
D. Electron Affinity
2. Why smaller going down?
a) e- further from the nucleus
b) Greater shielding; additional e- feel the
attraction from the nucleus less.
3. Why greater to the right?
a) Higher nuclear charge without greater
shielding; stronger nucleus has a greater
attraction for e- (atoms tend to make anions)
Examples
Which atom has the higher e- affinity?
K or Br
Br
F or I
F
E. Electronegativity
Electronegativity
1. Increases UP and to the RIGHT
1
2
3
4
5
6
7
F
Examples
If the following atoms were bonded
together, which would have the higher
electronegativity?
P or S
S
Se or O
O
F. Melting/Boiling Point
Melting/Boiling Point
Highest in the middle of a period.
1
2
3
4
5
6
7