Transcript ch5-PeriodicTable

Chemistry
Chapter 5
The Periodic table
The Periodic table
• Most valuable tool to
chemists
• Developed by Dimitri
Mendeleev
• Originally arranged by
increasing atomic mass
• Modern periodic chart is
arranged by increasing
atomic number
http://www.topspeed.tv/mrs.dem
aree/mendeleev.jpg
Periodic Law
• Rows are called periods
– Atomic mass and atomic number
increase across a period
• Columns are called Groups or
Families
– Elements in groups have the same
number of valence electrons
– Elements in the same group also
have similar chemical properties
• The pattern or repeating
properties is called PERIODIC
LAW
Periodic Trends
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Families
Atomic Radius
Ionization energy
Electronegativity
Reactivity
Webshots.com
Atomic Radius
• As atomic # increases, the
increasing # of protons attracts
valence electrons more closely
to nucleus.
• Within a period, atomic radius
decreases as atomic #
increases
Atomic Radius Trends
I
n
c
r
e
a
s
e
s
Atomic Radius Decreases
Ionization Energy
• Energy required to remove
an electron from an atom’s
outer energy shell.
• In a period, IE increases
as atomic # increases.
• In a group, IE decreases
as atomic # increases
Ionization Energy Trends
Electronegativity
• Ability of an atom to attract electrons to
itself in a compound.
• EN increases from lower left to upper right
of periodic table.
• (similar to ionization energy)
Electronegativity Trends
Reactivity
• How readily a substance
combines chemically w/another
substance
• Elements w/out full set of
valence electrons tend to react.
• Elements w/full set tend NOT to
react. (Noble Gases)
Noble Gases
Noble
Gases
Classes of elements
• Metals- on left of
periodic table
Titanium
• Nonmetals- right
Helium
• Metalloids- in
between
Germanium