The Periodic Table and Periodicity

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The Periodic Table and Periodicity
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Areas of Interest

• Mendeleevs brilliant organizational skills
• The modern table groups, families and series
  and trends

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Dimitri Mendeleev
The father of the periodic table. In the 19th
century elements were being discovered rapidly, a
way was need to organize them. He arranged the
atoms according to increasing atomic weight. Ok
so what? The brilliance of his arrangement came
from the atoms he left off the table . . . Those
that had not yet been discovered. Mendeleev
arranged his table in rows and columns that not
only addressed increasing atomic mass but was
able to predict undiscovered elements based on
properties.
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Mendeleev's Table
For years chemists had known about elements
sharing similar properties, in 1869 Dimitri
Mendeleev provided an organized arrangement. His
most famous omission he named eka-silicon. He
predicted an element that had a greater mass than
silicon, a smaller mass than tin but shared
similar properties with both elements.
Property Ekasilicon Germanium
atomic mass 72 72.59
density (g/cm³) 5.5 5.35
melting point (C) high 947
color gray gray
oxide type refractory dioxide refractory dioxide
oxide density (g/cm³) 4.7 4.7
oxide activity feebly basic feebly basic
chloride boiling point under 100C 86C (GeCl4)
chloride density (g/cm³) 1.9 1.9
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Moseleys Periodic Law
Henry Moseley determined the atomic number of
each element and placed them in order of
increasing atomic number, rather than atomic
weight. This atomic number arrangement also
followed Mendeleevs trends in properties.
Elements with similar properties were grouped
together. The modern period table was born
(1914).
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The Modern Periodic Table
Arranged in rows and columns. ? A row is called
a period ? A column is called a group or
family Some of the groups (or families) have
special names that help us identify them as a
collective. Famous families if you will . . .
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The Modern Periodic Table
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The Modern Periodic Table
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The Alkalai Metals
The include all of Group 1 Li, Na, K, Rb, Cs and
Fr. Soft shiny metals that react violently with
water to produce H2 gas. Electron configurations
of ns1. (ie Li is 1s22s1) Readily form 1
cations (ie Na loses and electron to form Na)
Francium only exists for microseconds so it
cannot be studied in quantity.
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The Alkaline Earth Metals
The include all of Group 2 Be, Mg, Ca, Sr and
Ba. These metals are soft but not quite as much
as those of Group 1. They are stable in air
(unlike the Alkalai Metals) Electron
configurations of ns2. (ie Be is 1s22s2) Readily
form 2 cations (ie Mg loses 2 electrons to form
Mg2)
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The Transition Metals
Electron-rich elements that most resemble what we
think of when we talk about metals ? theyre
malleable and ductile ? they conduct
electricity ? the free flow of electrons yields
many colorful solutions ? theyre shiny ? they
conduct heat
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Lanthanides and Actinides
Many of these elements are synthetic, theyre
made in particle accelerators and used for
research or highly specific purposes. They are
metals but they are very dense and many are quite
rare.
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The Metalloids
The metalloids
Elements include B, Si, Ge, As, Sb, Te and
At Theyre not quite metals but theyre not quite
non-metals. Theyre semi-conductors (they can
selectively conduct electricity).
Si, the semiconductor the computer industry is
built upon
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The Halogens
The Halogens
Elements include F, Cl, Br, I and At Readily
form -1 anions (ie Cl gains an electron to form
Cl-) React well with metals from Groups 1 and
2. Behave as other non-metals (non-conductive,
not shiny etc.)
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The Noble Gases
These are the elements found in Group 18, the
farthest to the right on the periodic table. They
are all gases and are VERY stable (they do not
readily undergo reaction). The have full energy
levels and sub-shells. For example Ar has
electron configuration 1s22s22p63s23p6. When we
pass a high-voltage current through any of these
gases we get extremely bright light.
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The Full Expanded Table
Metalloids and Non Metals
Metals
Transition Metals
Lanthanides Actinides
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• Use your textbook to define the following terms
• Atomic radius half the distance between 2
  nuclei in a covalent bond (an estimate of the
  radius of a single atom)
• 1st Ionization Energy the energy required to
  remove the 1st electron from an atom in the
  gaseous state (generating a 1 cation)
• 2nd Ionization Energy the energy required to
  remove the 2nd electron from a gaseous atom
  (generating a 2 cation)
• Electron Affinity the energy released when a
  gaseous atom captures an electron (generating a
  -1 anion)
• Electronegativity the tendency of an atom to
  attract electrons to itself (higher
  electronegativity means the atom wants
  electrons)
• Activity a trend that dictates replace-ability
  in single replacement reactions (decreases down
  the halogens)
• Valence Electron an electron in the highest
  occupied energy level of an atom (these are the
  ones involved in bonding)
• Effective Nuclear Charge the pull on the
  electrons from the protons in the nucleus
  (decreases as atoms get larger)

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Trends in the Table
Atomic Radius (Atomic Size)
Why this pattern? Decreasing effective nuclear
charge (the pull the electrons feel from the
protons in the nucleus)
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Atomic Radius Half the distance of a pure
covalent bond
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Trends in the Table
Atomic Radius (Atomic Size)
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Trends in the Table
1st Ionization Energy - the energy required to
remove 1 electron from a neutral atom
Ionization energy decreases down a
Group. Ionization increase from left to right in
a period.
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Trends in the Table
Increasing Electronegativity
Increasing Effective Nuclear Charge
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Your Assignment

• This element is larger than chlorine but smaller
  than iodine.
• Of the following pairs, which is MORE metallic
• Si or Ge
• As of Ge
• Ba or Cs
• Be or B
• Kr or Xe
• The electron configurations of six neutral atoms
  are shown
• 1s2 2s2 2p6 3s1
• 1s2
• 1s2 2s2 2p6 3s2
• 1s2 2s2 2p6
• 1s2 2s1
• 1s2 2s2 2p3
• Which has the highest first ionization energy?
• Which has the lowest first ionization energy
• Which would have the lowest second ionization
  energy?
• Which would likely have the lowest third
  ionization energy?