Transcript periodic table power point

The Periodic Table and Trends
of the Elements
By Diane Lunaburg
2001
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In this show you will learn about the most
important tools in chemistry--the periodic
table of elements.

Each element is made of a particular atom whose
properties depend on the structure of the atom.

The periodic table organizes the elements in a
way that shows periodicity, or uniform and
predictable changes of those properties.

If you can recognize the trends of the periodic
table, you do not need to memorize all the facts
about each element.
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History of the Periodic Table
 In 1869 A Russian chemist named Dmitri
Mendeleev organized the elements into a table that
became the basis of the modern
periodic table.
 He used the atomic weights
of the elements to arrange them.
He even predicted the existence
of elements based on gaps in the
sequence of the atomic weights.
 He also placed the elements in
columns to show periodic
similarities of the elements.
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The Modern Periodic Table
 In 1913 an English chemist named Henry Moseley
discovered the number of positive charges in the nucleus
of an atom and rearranged the periodic table using the
atomic number or number of protons in the atom.
 This also lead to what is know as:
The Periodic Law.
 This states that a periodic pattern appears in
the physical and chemical properties of the
elements when they are arranged in order of
increasing atomic number.
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The modern periodic table has about 109
known elements on it.
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Each box on the periodic table has
information about the element it
represents.
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Remember:
Atomic number:
The number of protons in the atom
Elemental Symbol: Always begins with a capital letter
Average atomic
mass:
and may be followed by lower
case letters. It represents the
element
The average of the naturally
occurring isotopes of each element.
Oxidation number: The charge acquired by an atom
when it gains or loses an
electron.
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The Periodic Table displays a variety of
physical properties
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The Periodic table arranges elements into a series
of vertical columns called groups or families
and horizontal rows called periods.
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What is a group or family?
Elements arranged in a vertical
column on the periodic table have
similar chemical properties
because they have the same
number of valence electrons,
electrons in the s and p orbital.
This is because the number of
valance electrons an atom has
governs how it behaves in
chemical bond. The characteristics
of elements within a group would
be more similar than elements
within a period.
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The valence electrons are the electrons in the outer
shell of an atom. According to the octet rule, an atom
wants a full outer shell and will gain or lose electrons to
make it happen. When they do they become charged.
The charge
they acquire
is called their
oxidation
number. All
noble gases
have full
outer shells
and are in
turn nonreactive.
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What is a Period?
The physical and chemical properties of elements
gradually change as you move across a period.
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The elements of the periodic table can be
grouped a number of ways as seen above.
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Remember the characteristics
of Metal?

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They are usually gray
solids at room
temperature
They are sometimes
lustrous
They are malleable and
ductile
they are good
conductors of heat and
electricity
They usually form
positive ions
 Ductile
Malleable
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The representative elements are also broken into
groups.
Hydrogen
The Alkali Metals
The Alkaline Earth Metals
The Halogens
The Noble Gases
Other Nonmetals
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Hydrogen
Hydrogen usually stands in a class by
itself. It is a colorless, flammable gas
at room temperature. It is like a
nonmetal at room temperature but
under extreme temperatures and
pressures it can behave like a metal.
It has one electron in its outer shell and will form an ion
with an oxidation state of +1. This is similar to the alkali
metal group so it is placed at the top of that group.
Sometime, however it is placed by itself at the middle of
the periodic table to indicate its uniqueness.
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The Alkali Metals
Group 1
The Alkali metals are group
1 on the periodic table.
They are usually soft dull
metals.
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They have one
valance electron
and usually have
an oxidation state
of +1
They are very
reactive with
oxygen or moisture
They dissolve
easily in water and
form basic
solutions
Alkali
Metals
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The Alkaline Earth Metals
Group 2
The alkaline earth metals
are group 2. They are
also soft and dull gray.
The Alkaline Earth Metals
are also fairly reactive
but do not dissolve as
easily in water. Because
of this they are often
found as deposits in soil.
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The Transition Metals
The transition metal are group 3-12. They
have metals that exhibit a variety of
properties from magnetic, orange luster, and
even liquid. They exist in a variety of
oxidation states
depending on
what they are
bonding with.
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The inner Transition Metals
The inner transition metals from 58-71 are the Lanthanide.
They are a part of period 6. They are very large atoms.
The inner transition metals from 90-103 are the Actinides.
They are part of period 7. All of the elements occurring after
Uranium are man made and most exist only for a short time
before decaying into more stable atoms.
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The Halogens
Group 17
The halogens are group 17. They
have 7 electrons in their outer shell.
They would like to gain 1 electron to
satisfy the octet rule. When they do
they gain a -1 oxidation state. They
usually bond with alkali metals to
form salts. By themselves, halogens
are diatomic molecules.
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The Noble Gases
Group 18
The noble gases are group 18.
They have a complete outer shell.
All elements have 8 electrons in
their outer shell except Helium.
Helium has only one s orbital and
therefore can only hold 2 electrons
which fills the orbital. Because they
satisfy the octet rule naturally they
are non-reactive or inert. They
exist as single atoms in a gas state
at room temperature.
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Other
Nonmetals
The rest of the elements may
be broken into their own
groups or spoken about
collectively.
Nonmetals have a variety of
colors, states and properties.
 They are brittle and poor
conductors of heat and electricity.
 They usually form negative ions to
satisfy the octet rule.
 They also tend to form
covalent bonds with
one another.

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Periodic Trends

Atomic Radii:
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Ionic Radii:
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Ionization Energy:

Electron Affinity:
The distance from the nucleus to
the outer edge of the electron cloud
The distance from the nucleus to the
edge of the electron cloud of an ion.
The amount of energy
needed to remove an electron from an atom
The energy change that
occurs when an atom gains an electron.

Electronegativity:
The ability of an atom to
attract electrons toward itself from a covalent
chemical bond.
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Atomic Radii
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Atomic Radii increases
as you go down a group
because of adding
energy levels.
Atomic Radii
decreases as
you go across a
period because
of an increasing
pull from the
added protons
of the nucleus.
+
Atomic
Radii
+
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Decrease
Smallest
I
n
c
r
e
a
s
e
Largest
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Ionization energy is the amount of energy
it takes to remove and electron from an
atom.
You will
notice it
takes more
energy to
remove
electrons
from
atoms that
almost
have their
octet or
have an
octet.
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Electron Affinity
Electron affinity is the amount of energy required
to capture an electron.
•If an atom has a negative (-) electron affinity it
mean it needs no energy and actually releases it
when an electron is captured.
•If an atom has a positive (+) electron affinity it
means it needs energy to capture an electron.
Atoms with an almost complete octet need little to
no energy to capture an electron.
Atoms with only 1 or 2 electrons in their outer shell
need a lot of energy to capture an electron.
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Electronegativity
Electronegativity is
usually important
when determining
if a covalent bond
would be polar or
non-polar. Very
high
Electronegativity
means the atom
will completely
capture the
electrons which
result in an ionic
compound.
+
-
Electronegativity is the
tendency of an atom to pull
electrons in a shared bond
closer to itself creating a bond
that is polar. Polar means
slightly more negative on one
side and slightly more positive
on the other.
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Electronegativity
Electronegativity of 0.0
to 0.4 is a covalent
bond.
Electronegativity of 0.4
to 2.1 is a polar bond.
Electronegativity of 2.1
to 4.0 is an ionic bond.
You must subtract the values of
electronegativity to determine it the
bond is covalent, polar covalent or
ionic
Covalent shares the
electrons equally
Polar is slightly
negative on one side
Ionic has electrons
captured by one atom.
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