Transcript Periodic Trends

Table of Contents
Lecture/Lab/Activity
14. The History of Atomic Models
15. Structure of the Atom
16. Isotopes
17. Beanium Lab
18. Electron Probability Lab
19. Electron Configuration
20. Orbital Diagrams
21. Electron Config Practice
22. The Periodic Table
23. Periodic Def & Trends
Date
9/14/10
9/15/10
9/16/10
9/17/10
9/20/10
9/21/10
9/22/10
9/23/10
9/24/10
9/27/10
Pg#
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Objective:
The student will label a periodic table to identify
and explain periodic trends including atomic radius,
electronegativity and ionization energy.
Agenda:
The Periodic Table– Lecture
Periodic Definitions & Trends
How to read the Periodic Table
6 Atomic Number
Elemental Symbol
C
Carbon Elemental Name
12.011 Atomic Mass
Definitions
• Atomic Number
• Is the same as the number of protons in an element.
• If this number changes the element name must change
as well.
• Atomic # = # of protons = # of electrons
• Atomic Mass
• Is a weighted average of all the atoms in a naturally
occurring sample of an element (mass & relative
abundance)
• 1 amu – one tweflth the mass of a carbon-12 atom
Calculating Neutrons
• Round the Atomic Mass
Atomic Mass
- Atomic Number
(difference = # neutrons)
Example:
6
Atomic Mass = 12
C
Atomic #
=
6
Difference
=
6
Carbon
12.011
Difference = # neutrons
Calculating Atomic Mass
• 3 values required:
• # of stable isotopes of an element
• The mass of each isotope
• The natural percent abundance of each isotope
• ? If Element X has 2 naturally occurring isotopes,
what is its atomic mass? Mass 1 = 10.012 amu and
has a relative abundance of 19.91 % , Mass 2 =
11.009 amu and has a relative abundance of
80.09%
Periodic Law
250
Atomic Radius (pm)
• When elements are
arranged in order of
increasing atomic
#, elements with
similar properties
appear at regular
intervals.
200
150
100
50
0
0
5
10
Atomic Number
15
20
Chemical Reactivity
• Families
• Similar valence e- within a group result in similar
chemical properties
1
2
3
4
5
6
7
Periodic Trends
• Atomic Radius
• size of atom
• 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
1
2
3
4
5
6
7
• Energy required to remove one e- from a
neutral atom.
• Increases going UP and to the RIGHT
Ionization Energy
• Why opposite of atomic radius?
• In small atoms, e- are close to the nucleus
where the attraction is stronger
• Why small jumps within each group?
• Stable e- configurations don’t want to lose e-
Electronegativity
• The attraction an element has on a shared
paired of electrons
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
Ionic Radius
• Cations (+)
• lose e• smaller
• Anions (–)
• gain e• larger
© 2002 Prentice-Hall, Inc.