Transcript Periodic Law

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Chapter 5:
Periodic Trends
The investigation and
understanding of the atom is what
chemistry is all about!
Topics rearranged from your
text. Over the next week, you
should read pages 73-134
Periodic Law:
…
©Bires, 2002
Slide 1
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The Periodic Table
• The Periodic Table
– a collection of all the known elements into a model
that groups elements with similar properties.
• Groups
– Vertical columns of elements with similar properties.
• Periods
– Horizontal rows of elements with atomic mass and
similar electron configurations.
©Bires, 2002
Slide 2
Periodic Table History
• Dmitri Mendeleev
Back
c 1869
– Russian chemist, ordered the known elements
according to properties and masses.
(Gaps?)
• Henry Moseley
c 1911
– arranged the elements according to atomic number
(# of protons).
– This is the system we use today.
• Periodic Law
– chemical and physical properties of elements are
periodic functions of their atomic numbers.
– The elements in the periodic table are arranged
according to Periodic Law (why He is over N.G.s)
©Bires, 2002
Slide 3
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Octets!
• Octets:
2
6
...s p ...
– filled s and p orbitals in the same, highest level.
– Have noble gas-like configurations
– Have special stability (atom’s goal).
• Both atoms and ions can have complete octets.
Ne  1s 2 2s 2 2 p 6 Ar  1s 2 2s 2 2 p 6 3s 2 3 p 6 S2-  [ Ne] 3s 2 3 p 6 Ca 2  1s 2 2s 2 2 p 6 3s 2 3 p 6
• Valence Electrons
– Electrons in the highest level (s and p)
– Given, taken, shared in chemical reactions
– creates trends in the properties of elements …
©Bires, 2002
Slide 4
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Periodic Trends – Atomic
Radii
• As electrons are added to the outside of atoms,
in the same period, the atom’s radius
decreases. Why?
• As new shells are added, radius increases.
Text Page 141
Smaller from left to right
©Bires, 2002
Slide 5
Periodic Trends –
Ionization Energy
Back
• Ionization Energy - the energy required to strip an
electron from an atom.
A  energy  A  e
• As more electrons are added to a shell, it’s more
difficult to remove them. (More protons pulling inward)
• Easier to remove electrons from larger atoms.
Text Page 143
Larger from left to right
©Bires, 2002
Slide 6
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Period Trends – Electronegativity
• Electronegativity (electron affinity)
– an atom’s ability to attract electrons
– Negative electron affinity = atom wants e-.
– Decreases down a group
Text Page 147
Larger from left to right
©Bires, 2002
Slide 7
Back
Ionic Radii
• +  - attraction determines the
atom’s radius.
• An electron is added to a
atom  e  anion()
nonmetal atom :
e– Anion is formed.
Cl
– Anions are larger than their neutral
Why?
atom
• An electrons is removed from a
metal atom:
e– Cation is formed.
– Cations are smaller than their
neutral atoms
©Bires, 2002
Cl-
Why?
Na
Na+
atom  e  cation()
Slide 8
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Groups and their Properties
• Recall:
– elements in the same group have similar properties
due to similar electron configurations.
• Learn the following group-families and their
basic chemical and physical properties:
– Alkali Metals
– Alkaline-Earth Metals
– Transition Metals
– Main-Block Elements
– Noble Gasses
– Rare-Earth Elements
©Bires, 2002
Slide 9
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Group 1 (+1)
Alkali Metals (s)
• soft, highly reactive metals.
• Lustrous
– will reflect light
• Electrically Conductive
– able to pass a charge through the material.
– often found in lights, batteries, and electrolytes.
• Low melting points
• Low density.

©Bires, 2002
ending e config  #s
1
Slide 10
Back
Group 2 (+2)
Alkaline-Earth Metals (s)
• Properties are similar to group 1 elements, but are:
• Harder
• Less reactive than Group 1 elements.
– (These elements are still very reactive.)
•
•
•
•
Lustrous
Electrically Conductive
Higher melting points than Group 1 metals.
More dense than Group 1 metals.
2
ending e config  #s

©Bires, 2002
Slide 11
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Groups 3-12 (various)
Transition Metals (d)
• This is where we find most metals, including the
coinage metals.
• Lustrous
• Electrically Conductive
• Malleable
– able to be shaped and formed, and hold that shape.
• Ductile
– able to be drawn into wires
• Very hard
• Very dense
• High melting points
©Bires, 2002
ending e

#
config  #d
Slide 12
Group 13-17 (+4-4)
Main-Block Elements (p)
Back
• The most varied elements.
– Liquids, gasses, and solids can be found in this
group. Have widely varied properties
• Includes Metalloids
– elements having properties of both metals and non
metals.
• Most elements necessary to living things are
found in this section.

ending
e
config

• Includes Halogens
#
#p
– Group 17 gasses and liquids F, Cl, Br, I, At
– are very reactive due to very high electron affinities.
©Bires, 2002
Slide 13
Group 18 (0)
Noble Gases (p)
•
•
•
•
•
Back
Mostly unreactive.

6
ending e config  # p
All have filled octets.
Near zero electron affinity
Very high ionization energies.
Noble gasses make up a trace amount of our
atmosphere
– are mined from pockets of gases in the oceans.
• When electrically charged:
– noble gases produce brilliant plasmas, often used in
signs.
Slide 14
©Bires, 2002
f – Group (various)
Rare earth metals (f)
Back
• Very heavy, dense (large nuclei)
• Most are radioactive.
• Lanthanides
– The first row, starting with lanthanum (57La)
– (4f elements)

• Actinides
#
ending e config  4or 5 f
– The second row, starting with actinium (89Ac)
– (5f elements)
• Transuranium elements
– All elements after Uranium 92U (93Np on) are artificial.
End of
Chapter
©Bires,
2002 5
Slide 15
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CCSD Syllabus Objectives
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6.1: Groups and Families
6.2: Periodic Law
6.3: Periodic Properties-Atomic Structure
6.4: Periodic Properties-Periodic Law
6.5: Groups and Trends
6.6: Metals, Nonmetals, Metalloids
6.7: Trends-atomic structures
6.8: Electron config-p-table location
7.4: Oxidation numbers
©Bires, 2002
Slide 16