Download Chapter Twelve: Atoms and the Periodic Table

Chapter Twelve: Atoms and the
Periodic Table
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12.1
12.2
12.3
12.4
The Structure of the Atom
Electrons
The Periodic Table of Elements
Properties of the Elements
What does a library, grocery store,
department store, and phone book
have in common?
The first periodic table
• Russian scientist Demitri Mendeleev
discovered a set of patterns that applied to all
the elements.
• Mendeleev noticed a pattern of properties
when he arranged the elements in order of
increasing atomic mass.
• Mendeleev used the melting point, density,
color, atomic mass, and number of chemical
bonds of elements to organize the periodic
table.
• Mendeleev arranged the elements in order of
increasing mass so that elements with similar
properties were in the same column.
• Mendeleev used the properties of existing
elements to predict properties of
undiscovered elements.
• The close match between Mendeleev’s
predictions and the actual properties of new
elements showed how useful his periodic
table could be.
• Periodic means “in a regular repeated
pattern.”
• In the periodic table, element properties
repeat in each row or period.
• British scientist Henry Moseley measured
elements by the size of their positive
charge (or the number of protons)
• The periodic table changed from being
organized by atomic mass to atomic
number.
12.3 The Periodic Table
• The periodic table organizes the elements according
to how they combine with other elements (chemical
properties).
• The periodic table is organized in order of increasing
atomic number.
12.3 The Periodic Table
• The periodic table is
further divided into
periods and groups.
• Each horizontal row is
called a period.
• Each vertical column is
called a group.