Back ©Bires, 2002 Slide 1 Bires, 2009 Chapter 5: Periodic Trends The investigation and understanding of the atom is what chemistry is all about! Topics

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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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

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Back ©Bires, 2002 Slide 1 Bires, 2009 Chapter 5: Periodic Trends The investigation and understanding of the atom is what chemistry is all about! Topics