The Periodic Table

1
The Periodic Table

• Chapter 5

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Newlands

• 1865
• Observed when elements arranged according to
  increasing atomic mass, the properties of the 8th
  element were like those of the 1st
• The pattern repeats every 8th element
• Called this the law of octaves

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Mendeleev

• 1869
• When he arranged the elements according to
  increasing atomic mass, he could see a periodic
  repetition of their properties
• Predicted properties of elements yet to be
  discovered
• Some inconsistencies

4
Moseley

• Worked in Rutherfords lab
• Determined atomic number
• Arranged his periodic table according to
  increasing atomic number

5
Periodic Law

• When elements are arranged in order of increasing
  atomic number, their physical and chemical
  properties show a periodic pattern.

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The Periodic Table

• The Modern Periodic Table
• elements listed in order of increasing atomic
  number
• Group
• a vertical column of elements
• contains elements with similar chemical
  properties
• Period
• a horizontal row of elements
• elements are not related chemically

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Group Names

• Group I (1) Alkali Metals (not including
  hydrogen)
• Group II (2) Alkaline Earth Metals
• Group VIIA(17) Halogens
• Group VIIIA (18) The Noble (Inert) Gases

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The Periodic Table

• Metals
• -luster or shiny -thermal and electrical
  conductivity -malleable and ductile
• Nonmetals
• -not lustrous or shiny
• Poor conductors of heat and electricity
• Brittle
• Metalloids
• -properties intermediate between those of
  metals and nonmetals

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Properties of metals

• Tend to be found on the left side of the PT
• Lustrous and shiny
• Thermally and electrically conductive
• Malleable
• Ductile
• Tend to react with acids
• Most are solids (except Hg)

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Properties of Nonmetals

• Tend to be found on the right side of the PT
• Are not lustrous or shiny
• Poor conductors of heat and electricity
• Neither malleable or ductile (tend to be brittle)
• Most are liquids and gases, but some are solids

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Properties of Metalloids

• Have some properties of metals and some
  properties of nonmetals
• Found along the stairstep in the p-block

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Periodic Trends

• Atomic Radius (size of an atom)
• Ionization Energy (energy needed to remove an
  electron)
• Electronegativity (ability to attract electrons
  in a chemical bond)

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Atomic Radius

• Down a group
• The larger the E level, the larger the atom
• Across a period
• Same E level, but increasing protons
• Atomic size decreases across a period

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Atomic Radii within a Group
Hydrogen (1 proton) 1st E level
Lithium (3 protons) 2nd E level
Sodium (11 protons) 3rd E level
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Boron (5 protons) n 2
Beryllium (4 protons) n 2
Lithium (3 protons) n 2
If protons were light bulbs.and electrons were
moths...
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Boron (Z5)
Beryllium (Z4)
Lithium (Z3)
?Increasing
?Increasing
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First Ionization Energy
Hydrogen (1 p)
Lithium (3 p)
Sodium (11 p)
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First Ionization Energy
Hydrogen (1 p)
e-
?Decreasing
Lithium (3 p)
2e-
e-
Sodium (11 p)
2e-
8e-
e-
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e-
e-
2e-
2e-
2e-
e-
e-
e-
e-
Boron (Z5) 5 protons screened by 2 e-
Beryllium (Z4) 4 protons screened by 2 e-
Lithium (Z3) 3 protons screened by 2 e-
1 e- removed 2s0
1 e- removed 2s22p0
1 e- removed 2s1
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2e-
e-
2e-
e-
e-
Boron (Z5) 5 protons screened by 2 e-
Beryllium (Z4) 4 protons screened by 2 e-
Lithium (Z3) 3 protons screened by 2 e-
?Decreasing
?Decreasing
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Trends in the Periodic Table
Atomic Radii (Size)
?Increasing
?Increasing
First Ionization Energy
?Decreasing
?Decreasing
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Ionization Energy

• You can think of ionization energy as a
  reflection of how strongly an atom holds onto its
  valence electrons.
• If an atom has a high IE, it holds onto its
  electrons very tightly.
• If an atom has a low IE, it holds onto its
  electrons very loosely.

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Electronegativity

• Desire to gain an electron
• Across a period, it increases
• Down a group it decreases.