The Periodic Table

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The Periodic Table
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A. History of the Periodic Table

• 1. First developed by Dmitri Mendeleev in 1869.
• 2. Mendeleev was looking for a way to arrange the
  elements.
• 3. As he studied properties such as atomic mass,
  he noticed a repeating pattern.

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Side Note What does Periodic mean??

• Periodic means repeated in a pattern!
• HOWEVER, Mendeleev had to leave some spaces
  because not all elements lined up according to
  atomic mass. Notice that he used his information
  to PREDICT masses. Very scientific!

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B. The Modern Periodic Table

• 1. c. 1914 Henry G.J. Moseley realized that
  elements could be arranged according to atomic
  NUMBER rather than mass.

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2. Seaborg (1944)

• a. rearranged Periodic Table with...
• Lanthanide and Actinide Series pulled
  out/separated from main Periodic Table
• b. discovered 10 new elements countless isotopes

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B. Arrangement of the PT
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• 1. The boxes are arranged into vertical columns
  called groups or families. They are numbered 1 -
  18.
• a. The group numbers tell us the number of
  electrons in that elements outer energy level -
  the number in red

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15
17
14
13
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b. valence electrons

• electrons found in the outermost energy level

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c. Octet Rule

• We just said that the red number in the
  family/group number the number of electrons in
  the outer shell or valency.
• Octet Rule The tendency of atoms to gain or lose
  electrons so they acquire eight electrons in
  their outer energy level.

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d. Groups to Know

• Group 1 - Alkali Metals
• Group 2 - Alkaline Earth Metals
• Group 17 - Halogens
• Group 18 - Noble Gases

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2. Periods

• a. The boxes are arranged into horizontal rows
  called periods.
• b. The period numbers tell us the number of
  energy levels that an atom has
• c. Periods are numbered 1 through 7

1
2
3
4
5
6
7
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3. Regions of the Periodic Table

• a. Metals - to the left of the stair-step line
• b. Non-Metals - to the right of the stair-step
  line
• c. Metalloids - on the stair-step line

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a. Metals

• Found to LEFT of zigzag line on table
• Good conductors of heat electricity
• Malleable
• Ductile
• High melting points
• Shiny
• Tend to lose electrons

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b. Nonmetals

• Found to RIGHT of zigzag line on table
• Poor conductors of heat electricity
• Brittle when solid
• Dull
• Low melting points
• Tend to gain electrons

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c. Metalloids/Semi-Metals

• Found along both sides of zigzag line
• Properties of both metals nonmetals
• Okay conductors of heat electricity
• Shiny or dull

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C. Trends in the Periodic Table

• Valence number
• Charge of ion (positive or negative)
• Tendency to gain or lose electrons
• Metallic vs. nonmetallic properties
• Atomic size (radius)
• Ionization energy
• Electronegativity (which ones WANT electrons the
  most)

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1. Across a Period

• radius decreases (size of atom gets smaller)
• ionization energy increases
• electronegativity increases
• b/c
• number of valence electrons increases
• so EMF increases
• so valence electrons held more tightly

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2. Down a Family

• radius increases
• ionization energy decreases
• electronegativity decreases
• b/c
• number of energy levels increases
• so valence electrons held less tightly