Chapter 5 : The Periodic
Table
Objectives

Be able to define and explain each
periodic trend, including comparing two
different elements. For example: which of
the following elements has the larger
atomic radius?
History of the Periodic Table
 In
the 1700s
scientists had
identified only 30
elements
 In the 1800s
there were 60
History of the Periodic Table
 Early
1800s
Dobereiner grouped
elements into triads
by physical and
chemical properties
 Li, Na, K
History of the Periodic Table
 1865
J.A.R. Newlands
discovered that when
elements were
arranged by atomic
mass, properties
repeated themselves
every eighth element
 Called these octaves
Mendeleev
 1869
Dmitri Mendeleev
produced the first
periodic table for his
students
 Left blanks where
elements had yet to be
discovered
 Not strictly in order of
atomic mass (Ar K)
Properties of Germanium as Predicted by
Mendeleev
Properties of
Ekasilicon
Atomic weight
Density
Specific heat
Melting point
Oxide formula
Oxide density
Chloride formula
bp of chloride
Predicted
in 1871
72
5.5 g/cm3
0.31 J/(°C · g)
Very high
RO2
4.7 g/cm3
RCl4
100°C
Properties of
Germanium
Atomic weight
Density
Specific heat
Melting point
Oxide formula
Oxide density
Chloride
formula
bp of chloride
Predicted
in 1871
72
5.5 g/cm3
0.31
J/(°C · g)
Very high
RO2
4.7 g/cm3
RCl4
100°C
Observed in
1886
72.3
5.47 g/cm3
0.32
J/(°C · g)
960°C
GeO2
4.70 g/cm3
GeCl4
86°C
Moseley
 In
1913 Moseley assigned
elements atomic numbers
and rearranged periodic
table
 Periodic Law – when
arranged by increasing
atomic number elements
show periodic trends
Table Terms
 Groups
or Families are the columns
on the periodic table
 Periods are the rows going across.
Periodic Properties

Depend on two main factors: the number
of protons and electrons, and the way
these subatomic particles interact with
each other.
Draw a Bohr Model for
Lithium
 Potassium
 Fluorine
 Make sure to indicate the number of
protons in the center
 Make sure levels are the same size from
atom to atom (rings for energy levels
should be the same size)

Lithium
Potassium
Fluorine
Atomic Radius

Atomic radius is the distance from the atom’s nucleus to its
outer edge.
 Simply can be thought of as the size of an atom
 Using the Bohr model, and thinking about the number,
arrangement, and interaction of the protons and electrons,
answer the following questions, and explain your answers
 Which atom has a larger atomic radius: lithium or
potassium?
 Which atom has a larger atomic radius: lithium or fluorine?
 What is the atomic radius ____ from left to right on the
periodic table.
 What is the atomic radius ____ from top to bottom on the
periodic table.
Atomic Radius
Atoms get larger going down a group or
family
– Principle energy level increases moving
down
 Atoms get smaller moving from left to
right
– In the same energy level, more protons
exert a stronger pull towards the
nucleus

Ionization Energy





Ionization energy is the energy needed to
remove one electron
Na(g) -> Na+(g) + 1eRemember that an ion is a atom with an overall
charge of negative or positive (number of
electrons changes)
Metals are more likely to give up an electron
than nonmetals.
The more difficult it is to remove an electron the
higher the ionization energy will be.
Ionization





Using the Bohr models, and thinking about the number,
arrangement, and interaction of the protons and
electrons, answer the following questions, and explain
your anwsers.
Which atom has a higher ionization energy: lithium or
potassium?
Which atom has a higher ionization energy: lithium or
fluorine?
Ionization energy______ from left to right on the
perioidic table
Ionication energy _______from top to bottom on the
periodic table
Ionization Energy

Ionization energy is the energy needed to
remove one electron
 Na(g) -> Na+(g) + 1e Metals are more likely to give up an electron
than nonmetals.
 IE decreases when moving down the group
 IE increases moving from left to right in a
period
 There are second and third IEs for the next
electrons
Electron Affinity

Electron affinity is the energy change that
occurs when an atom gains an electron
 F(g) + e-  F- (g)
 Most atoms give off energy when an electron
is gained (negative)
 Nonmetals have more of an electron affinity
than metals
 Atoms with greater affinity are more able to
gain valance electrons
Electron Affinity





Using the Bohr models, and thinking about the number,
arrangement, and interaction of the protons and
electrons, answer the following questions, and explain
your answers.
Which atom has a greater electron affinity: lithium or
potassium?
Which atom has a greater electron affinity: lithium or
fluorine?
Electron affinity _______ from left to right on the
periodic table.
Electron affinity ______from top to bottom on the
periodic table
Electron affinity
 EA
decreases when moving down the
group
 EA increases moving from left to right
in a period
Electronegativity






Electronegativity reflects an atom’s ability to attract
electrons
It is defined as the ability of an atom in a molecule to attract
electrons.
Example: if a molecule consists of atoms X bonded to atom
Y.
X-Y
The two atoms share the electrons in the molecule. If X is
more electronegative than Y, then the electrons will be more
strongly attracted to X than Y, and will “hog” the electrons
X–Y
Electronegativity
Which atom has a greater
electronegativity: lithium or potassium?
 Which atom has a greater
electronegativity: lithium or fluorine?
 Electronegativity _______ from left to
right on the periodic table.
 Electronegativity______ from top to
bottom on the periodic table

Electronegativity
 Cs
& Fr have the lowest
electronegativities; F has the
highest
 EN decreases when moving down
the group
 EN increases when moving from
left to right across the period
Ionic Radius

Ionic radius is the distance from the ion’s
nucleus to its outer edge.
 Remember that positive ions are formed
when atoms lose electrons
 Negative ions are formed when atoms gain
electrons
 Ions get larger going down a group or family
 Ions get larger moving from left to right
– The more electrons added increases repulsion
among them
Draw the Bohr models for the
following:







Lithium and Lithium ion (+)
How does the lithium ion’s radius compare to the
radius of neutral lithium?
Chlorine and Chlorine ion (-)
How does the chloride ion’s radius compare to
the radius of neutral chlorine?
Sodium ion (+) and Fluoride Ion (-)
How do the number of electrons in these two
ions compare to each other?
How do the radii of these two ions compare to
each other?
Ionic radius
 Ions
get larger going down a
group or family
 Ions get larger moving from left
to right
–The more electrons added increases
repulsion among them
Major Groups on the Periodic Table
 Alkali
Metals
 Alkaline Earth
Metals
 Transition Metals
 Boron Group
 Carbon Group
 Nitrogen Group
 Oxygen
Group
(Chalcogens)
 Halogens
 Noble Gases
 Actinide Series
 Lanthanide
Series
Reactivity of Alkali and Alkaline
Earth Metals
 Metals
become more
reactive as you
move down the
group
 Metals become less
active when moving
left to right
Why Are There Patterns?
 Elements
have physical and chemical
properties based upon their valence
electrons.
 Valence electrons are the electrons in
the outer most energy level (s & p
orbitals)
 The number of valence electrons may
be determined by using the periodic
table
Why Are There Patterns?
 When
you look at an atom you are
observing the valence electrons
 Duet rule - only 2 electrons fill the first
energy level
 Octet rule – 8 valence electrons is
considered to be a full set