Transcript Introduction to the Periodic Table

Chapter 3
Introduction to the Periodic Table
Section 3.1 Development of the Periodic Table
Section 3.2 Using the Periodic Table
3.1 Development of the Periodic Table
Objectives
 Outline the steps in the historical
development of the periodic table.
 Predict the similarities of properties of
elements by using the periodic table.
New Vocabulary to Look for…
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Periodicity
Periodic law
Searching for a Periodic Table
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By 1860 scientists had discovered 60
elements and determined their atomic
masses.
They noticed that some elements had similar
properties.
Copper, Silver and Gold- coinage metals
Lithium, Sodium and Potassium- alkali metals.
Chlorine, Bromine and Iodine- halogens
Döbereiner’s Triads
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Chemists wanted to organize the elements
into a system.
Döbereiner was the first to classify some
elements into groups of three.
The halogen triad, metal triad
Triads were useful
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Grouped elements with similar properties.
Revealed an orderly pattern to some physical and
chemical properties.
Suggested properties were related to the atomic
mass
Mendeleev’s Periodic Table
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Dmitri Mendeleev was a Russian
chemist and professor.
1869 he published his first table of
elements organized by atomic mass.
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Listed in vertical columns starting with the
lightest.
Elements with similar properties were
placed in horizontal rows.
Mendeleev’s Periodic Table
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He later developed an improved
version.
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Elements arranged in horizontal rows
Forerunner to the modern periodic table.
Patterns of changing properties repeated
for the elements across the horizontal
rows.
Elements in the vertical columns showed
similar properties.
Mendeleev
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His insight was a significant contribution to
chemistry.
He showed that properties of elements repeat
in an orderly way from row to row of the
table.
Periodicity-the tendency to recur at regular
intervals
Mendeleev predicted the properties of
undiscovered elements.
Mendeleev’s Predictions
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Called the elements eka-silicon and ekaaluminum.
Based on their location on his table he
predicted several of their properties.
He was correct:
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Eka-aluminum was discovered in 1875 and called
gallium
Eka-silicon was discovered in 1886 and called
germanium.
Mendeleev’s confidence
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He was so confident about his table that he
placed some elements with groups with
similar properties even though the atomic
masses were not in order.
Tellurium- he assumed the atomic mass was
wrong.
He was right on its placement, but wrong
about the atomic mass
Modern Periodic Table
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It now has about 118 elements
arranged in groups with similar
properties.
Transition elements, lanthanides,
actinides and noble gases were
unknown at Mendeleev’s time, but are
found on today’s table.
Element Block
Periodic Law
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The statement that the physical and
chemical properties of the elements
repeat in a regular pattern when they
are arranged in order of increasing
atomic number.
Review
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4.
Döbereiner arranged his elements in groups
of how many elements? This grouping was
based on what information?
Mendeleev predicted the properties of what
two undiscovered elements?
What led to the wide spread acceptance of
Mendeleev’s table?
Sodium and Potassium react violently with
water. How would you expect Rubidium to
react with water?