back ©bires, 2002 slide 1 bires, 2009 chapter 5: periodic trends the investigation and...
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©Bires, 2002 Slide 1Bires, 2009
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:
…
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©Bires, 2002 Slide 2Bires, 2009
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.
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©Bires, 2002 Slide 3Bires, 2009
Periodic Table History• Dmitri Mendeleev
– Russian chemist, ordered the known elements according to properties and masses. (Gaps?)
• Henry Moseley– 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)
c 1869
c 1911
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©Bires, 2002 Slide 4Bires, 2009
Octets!• Octets:
– 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.
• Valence ElectronsValence Electrons– Electrons in the highest level (s and p)– Given, taken, shared in chemical reactions– creates trends in the properties of elements …
622 221Ne pss 62622 33221Ar pspss 6233]Ne[-S2 ps 626222 33221Ca pspss
...... 62 ps
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©Bires, 2002 Slide 5Bires, 2009
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
Atomic Radii.mov
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©Bires, 2002 Slide 6Bires, 2009
Periodic Trends – Ionization Energy• Ionization Energy - the energy required to strip an
electron from an atom.• 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
eAenergyA
Ionization Energy.mov Second Ionization Energy.mov
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©Bires, 2002 Slide 7Bires, 2009
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
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©Bires, 2002 Slide 8Bires, 2009
Ionic Radii• + - attraction determines the
atom’s radius.• An electron is added to a
nonmetal atom :– Anion is formed.– Anions are larger than their neutral
atom
• An electrons is removed from a metal atom:– Cation is formed.– Cations are smaller than their
neutral atoms
)( anioneatom
Cl Cl-
Na Na+
)( cationeatom
Why?
Why?
e-
e-
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©Bires, 2002 Slide 9Bires, 2009
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
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©Bires, 2002 Slide 10Bires, 2009
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.
1#sconfigeending
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©Bires, 2002 Slide 11Bires, 2009
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#sconfigeending
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©Bires, 2002 Slide 12Bires, 2009
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
##dconfigeending
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©Bires, 2002 Slide 13Bires, 2009
Group 13-17 (+4-4)Main-Block Elements (p)
• 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.
• Includes Halogens– Group 17 gasses and liquids F, Cl, Br, I, At– are very reactive due to very high electron affinities.
## pconfigeending
Physical Properties of Halogens.MOV
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©Bires, 2002 Slide 14Bires, 2009
Group 18 (0)Noble Gases (p)
• MostlyMostly unreactive.
• 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.
6# pconfigeending
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©Bires, 2002 Slide 15Bires, 2009
f – Group (various)Rare earth metals (f)
• Very heavy, dense (large nuclei)
• Most are radioactiveradioactive.
• Lanthanides– The first row, starting with lanthanum (57La)
– (4f elements)
• Actinides– The second row, starting with actinium (89Ac)
– (5f elements)
• Transuranium elements– All elements after Uranium 92U (93Np on) are artificial.
#54 forconfigeending
End of Chapter 5
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©Bires, 2002 Slide 16Bires, 2009
CCSD Syllabus Objectives• 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