A Good Mystery

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CHAPTER 6
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A Good Mystery
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The mystery solved
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A hidden pattern uncovered
Dmitri Mendeleev 1834-1907
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How did he do it?

• Group the 63 known elements by their physical
  properties
• Find their bonding power (valence e-)
• Arrange by increasing atomic MASS
• He found a repeating pattern every 7(?) elements
• 1 2 3 4 3 2 1

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Valence electrons
1
2
3
4
3
2
1
0
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What was missing???
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and the elusive element 32
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By atomic mass does it work?
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The Modern Periodic Table
Periodic Law
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The Design
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FAMILIES
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Review How many electrons in outer shell?
Periodic Law
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Valence electrons (again)
1
2
3
4
3
2
1
0
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Families (groups)
All families are related
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Periods (Rows)
A pattern across
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Metals/Nonmetals and Metalloids
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Element Key
Atomic number
Element symbol
Full name of element
Phase at room temp
Atomic mass (average)
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Metals

• What comes to mind?
• Most of the 109 elements are metals
• Weakly held outer e-
• Properties of metals
• Good conductors of heat and electricity (p)
• High density (p)
• High melting points (p)
• Luster (p)
• Malleable (p)
• Ductile (p)
• Corrosive (c)

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Nonmetals

• Opposite of metals
• Properties of nonmetals
• Dull (no luster)
• Do not conduct heat
• Not ductile
• Not malleable
• All phases
• Form many compounds with metals

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Metalloids

• Means metal-like
• Dividing line b/w metals and nonmetals
• Properties of both metals and nonmetals
• Al is the exception
• Can you name all 8 of the metalloids?

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Meet the Fam...Or families, (in this case) ?
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Remembervalence e-
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• What makes a family a family?
• Similar properties
• Valence electrons
• 18 families
• Groups
• Active metals
• Transition metals
• Metals to non-metals
• Boron family
• Carbon family
• Nitrogen family
• Oxygen family
• Halogens
• Noble gases
• Rare-earth elements

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Most Active Metals

• Family 2 ? alkaline earth metals
• 2 valence electrons (tends to lose them)
• Not quite as reactive as alkali metals
• But still very reactive and also not found
  free in nature
• Mg and Ca familiar

• Family 1 ? alkali metals
• Exclude hydrogen
• 1 valence electron (tends to lose it)
• Soft, silvery white, shiny
• Bond easily
• Hate water ?
• Never found free in nature

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Transition Metals
Family

• Families 3 thru 12
• Properties are similar to each other
• Well known elements
• Good conductors
• 1 or 2 valence electrons
• Lose one or both
• Weird Can lose an e- from the next to outer shell

3
4
5
6
7
8
9
10
11
12
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Boron Family

• Family 13
• 3 valence electrons
• Boron is metalloid (rest are metals)
• Used in borax and heat resistant glass
• Al is most abundant metal in Earths crust
• Bauxite Al oxide

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Carbon Family

• Family 14
• 4 valence electrons
• All groups (1-2-2)
• 5 million compounds!
• Silicon
• Germanium
• Tin
• Lead

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Nitrogen Family

• Family 15
• 5 valence electrons
• Tend to share electrons in bonding
• Nitrogen is very stable

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Oxygen Family

• Family 16
• 6 valence electrons
• Share in bonding
• Oxygen most abundant element in Earths crust
• Extremely reactive!
• Sulfur
• Selenium
• Tellurium
• Polonium very rare

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The Halogens

• Family 17
• 7 valence electrons
• Most active non-metals
• Most are poisonous
• Gain 1 electron in bonding
• Never found free in nature

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Noble Gases

• Family 18
• 8 valence electrons
• Full outer shell
• All non-reactive gases
• Helium
• Neon
• Argon
• Krypton
• Xenon
• Radon

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The Rare-Earth Elements

• Lanthanoid series
• Atomic 57 to 70
• All have similar properties to each other
• Soft, malleable metals
• Used to make alloys and high quality glass

• Actinoid series
• Atomic 89 to 102
• All radioactive
• Only Th (90) and U (92) occur naturally
• Elements 104 are also radioactive

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Periodic Properties of the Elements
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PERIODIC TRENDS
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Reactive Metal ? Nobel Gas
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