Transcript Periodic Table

Organizing the Elements
History of the Periodic Table
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1860’s a Russian Scientist named Dmitri
Mendeleev discovered a system for
organizing all of the known elements.
To help him find a pattern he put all of
the known information on individual
cards.
He listed the elements
known properties.
Individual Properties Listed
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Known properties were: melting point,
density, color, atomic mass, # of
chemical bonds an element can form.
Atomic mass is the average mass of one
atom of that element.
Mendeleev’s Periodic Table
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Patterns appeared when elements were
arranged in order of increasing atomic
mass.
However, this did not always produce
similar groups. So he moved the cards
into the group it best fit.
This left blank spaces on the table.
Mendeleev’s Periodic Table
Mendeleev’s Periodic Table
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Mendeleev predicted that that the blank
spaces would be filled by elements that
had not yet been discovered.
He even predicted the properties of
new elements.
Published his table in 1869 the new
elements were discovered within 16
years.
Modern Periodic Table
Periodic – means regular,
repeated pattern.
Modern Periodic Table
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Properties are repeated in each period
or row of the table.
Elements are arranged by increasing
atomic number – not mass as
Mendeleev had previously thought.
Reading the Periodic Table
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- atomic number
Fe
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- elements symbol
Iron
55.847
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-elements name
Atomic mass
Organization of the Table
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An elements properties can be
predicted from its location on the table.
Across the row or down a column the
elements’ properties change in a
predictable way.
Groups or Families
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Elements in a column.
Numbered 1 on left to 18 on right.
Elements in a group have similar
characteristics.
They have the same number of valence
electrons.
Periods or Rows
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Contains a series of elements from
different families.
The elements have very different
properties.
7 periods of elements.
7 electron shells
Why it works
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The table works because it is based on
the structure of atoms, especially the
valence electrons.
Atomic # increases by 1, so it has 1
more valence electron than the previous
family.
and it has one more proton than the
previous atom.