The Periodic Table and Periodicity

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The Periodic Table and Periodicity
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Areas of Interest

• Mendeleev and his brilliant organizational skills
• The modern table groups, families and series
• Trends

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Dimitri Mendeleev
The father of the modern periodic table. In the
19th century elemenets 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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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 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, P, As, Se, and Te
(sometimes Al, Ge and Sb make the cut) 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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Trends in the Table
Atomic Radius (Atomic Size)
Increases down a Group. Decreases from left to
right in a period.
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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
Electron Affinity - the energy released when an
atom gains an electron forming a -1 anion
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Trends in the Table
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