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Chapter 5
The Periodic Table
Objectives
• Describe how Mendeleev arranged
the elements in his table.
• Explain how the predictions
Mendeleev made and the discovery of
new elements demonstrated the
usefulness of his periodic table
The Meaning of Periodic
• Having or marked by repeated cycles.
• Happening or appearing at regular
intervals.
• Recurring or reappearing from time
to time; intermittent.
Dmitri Mendeleev
1860’s
Only 63
elements
were known
at that time
Mendeleev’s Proposal
Mendeleev arranged the elements
into rows in order of increasing
mass so that elements with
similar properties were in the
same column.
Periodic Table
An arrangement of elements in
columns, based on a set of
properties that repeat from row
to row.
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Mendeleev’s Periodic Table
• Not a complete periodic table
• Had to leave spaces in his table
• Arrange elements by their mass
• Placed element with similar
properties in the same column
• Was able to predict properties of
elements yet to be discovered
Gallium
Mendeleev’s prediction:
Soft metal
Low melting point
Density of 5.9 g/cm3
Discovery of gallium (1875):
Soft metal
Melting point = 29.7C
Density = 5.91 g/cm3
Objectives
• Describe the arrangement of
elements in the modern periodic
table.
• Explain how the atomic mass of
an element is determined and
how atomic mass units are
defined.
• Identify general properties of
metals, nonmetals, and
metalloids.
The
Modern Periodic Table
The elements are arranged by
increasing atomic number
(number of protons)
Period
A row in a periodic table of
elements
Group
A column of elements in a
periodic table
Note: Properties of elements
repeat in a predictable way
when atomic numbers are
used to arrange elements into
groups.
Periodic Law
The pattern of repeating
properties displayed by
elements in the periodic
table
Atomic Mass
A value that depends on the
distribution of an element’s
isotopes in nature and the
masses of those isotopes
Atomic Mass Unit (amu)
One twelfth (1/12) the mass
of a carbon-12 atom
Chlorine
Isotope
Percent found
in nature
Atomic Mass
(AMU)
Chlorine-35
75.78%
34.969
Chlorine-37
24.22%
36.966
Classes of Elements
1. Metals
2. Nonmetals
3. Metalloids
Metals
Elements that are good
conductors of heat and
electric current
Most metals are malleable
and ductile
Metals (blue)
Transition Metals
Elements that form a bridge
between elements on the
left and right sides of the
periodic table
Transition Metals
Nonmetals
Elements that are poor
conductors of heat and electric
current
Note: Many nonmetals have a low
melting point which causes them
to be gases at room temperature.
Nonmetals (yellow)
Metalloids
Elements with properties that fall
between those of metals and
nonmetals
Note: A metalloid’s ability to
conduct electric current varies
with temperature.
Metalloids (pink)
Variation Across a Period
From right to left, elements
become more metallic and
less nonmetallic in their
properties
Variation Across a Period
Objectives
• Relate the number of valence
electrons to groups in the
periodic table and to properties
of elements in those groups.
• Predict the reactivity of some
elements based on their
locations within a group.
• Identify some properties of
common A group elements.
Valence Electron
Note About Valence
Electrons
Alkali Metals
Alkali Metals
Alkaline Earth Metals
Alkaline Earth Metals
Magnesium
Calcium:
-
The Boron Family
The Boron Family
 Metalloid (boron)
 Metal (aluminum)
 Metal (gallium)
 Metal (indium)
 Metal (thallium)
The Boron Family
Aluminum
-
The Carbon Family
The Carbon Family
 Nonmetal (carbon)
 Metalloid (silicon)
 Metalloid (germanium)
 Metal (tin)
 Metal (lead)
The Carbon Family
Carbon:
-
Silicon:
-
The Nitrogen Family
The Nitrogen Family
 Nonmetal (nitrogen)
 Nonmetal (phosphorus)
 Metalloid (arsenic)
 Metalloid (antimony)
 Metal (bismuth)
The Nitrogen Family
Nitrogen & Phosphorus:
-
The Oxygen Family
The Oxygen Family
 Nonmetal (oxygen)
 Nonmetal (sulfur)
 Nonmetal (selenium)
 Metalloid (tellurium)
 Metalloid (polonium)
The Oxygen Family
Oxygen:
Sulfur:
-
Halogens
Halogens
 Nonmetal (fluorine)
 Nonmetal (sulfur)
 Nonmetal (bromine)
 Nonmetal (iodine)
 Metalloid (astatine)
Halogens
Halogens
Fluorine:
Chlorine:
-
Noble Gases
Noble Gases