Transcript Organizing the Elements

Organizing the Elements
History of the Periodic Table
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1860’s a Russian Scientist named Dmitri
Mendeleev discovered a system for
organizing all of the known elements.
To help him find a pattern he put all of
the known information on individual
cards.
He listed the elements
known properties.
Individual Properties Listed
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Known properties were: melting point,
density, color, atomic mass, # of
chemical bonds an element can form.
Atomic mass is the average mass of one
atom of that element.
Mendeleev’s Periodic Table
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Patterns appeared when elements were
arranged in order of increasing atomic
mass.
However, this did not always produce
similar groups. So he moved the cards
into the group it best fit.
This left blank spaces on the table.
Mendeleev’s Periodic Table
Mendeleev’s Periodic Table
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Mendeleev predicted that that the blank
spaces would be filled by elements that
had not yet been discovered.
He even predicted the properties of
new elements.
Published his table in 1869 the new
elements were discovered within 16
years.
Modern Periodic Table
Periodic – means regular,
repeated pattern.
Modern Periodic Table
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Properties are repeated in each period
or row of the table.
Elements are arranged by increasing
atomic number – not mass as
Mendeleev had previously thought.
Reading the Periodic Table
26
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- atomic number
Fe
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- elements symbol
Iron
55.847
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-elements name
Atomic mass
Organization of the Table
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An elements properties can be
predicted from its location on the table.
Across the row or down a column the
elements’ properties change in a
predictable way.
Groups or Families
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Elements in a column.
Numbered 1 on left to 18 on right.
Elements in a group have similar
characteristics.
They have the same number of valence
electrons.
Periods or Rows
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Contains a series of elements from
different families.
The elements have very different
properties.
7 periods of elements.
7 electron shells
Why it works
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The table works because it is based on the
structure of atoms, especially the valence
electrons.
Atomic # increases by 1, so it has 1 more
valence electron than the previous family.
Atomic # increasing by 1 means it has one
more proton than the previous atom.
Metals
Metals
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Found on the left of
the zig-zag line.
Metals based on
physical properties
of hardness,
shininess,
malleability, ductility.
Physical Properties of metals
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Malleability means
that it can be
pounded into
shapes.
Physical Properties of metals
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Ductility means that
the metal can be
pulled out or drawn
into a long wire.
Physical Properties of metals
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Conductors – most
metals can transmit
heat and electricity
easily.
Magnetic – several
metals can be made
into magnets or are
attracted to
magnets.
Chemical Properties of Metals
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Some very reactive – sometimes
explosive others not reactive at all.
Metals on the left of the table Family 1
are the most reactive and they become
less and less as you move right.
Alloys
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Mixture of metal.
Useful alloys combine the best
properties of two or more metals into a
single substance.
Metals in the Periodic Table
Alkali
Alkaline Transition Mixed
Lanthinide
Earth
Metals
Groups Actinide
Family
1
Family
2
Families 3
-12
Alkali Metals
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Most reactive metals
Never found alone in
nature, always in a
compound.
Soft, shiny,
Sodium is an
example.
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Why are they so
reactive?
Because they have
one valence electron
that they can easily
give away.
Alkaline Earth Metals
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Group 2
Not as reactive as Group 1 but more
reactive than most metals.
Hard, bright white, good conductors of
electricity.
Each has 2 valence electrons which they
easily lose.
Transition Metals
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Group 3 – 12
Form a bridge between the very
reactive metals on the left side and the
less reactive metals on the right.
Very similar so that it is difficult to
detect differences from one column to
the next.
Transition Metals
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Fairly stable, reacting slowly or not at
all with air and water.
Used to make colorful paints such as
cobalt blue.
Iron, Cobalt, Nickel
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First elements in groups 8,9, 10 called
the iron triad.
The only ones known to create a
magnetic field.
Metals in Mixed Groups
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Groups 13 – 16 include: metals,
nonmetals, metalloids.
The metals to the right of the transition
metals are not as reactive as Groups 1
&2.
Lanthanides & Actinides
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Bottom of the periodic table are the
Lanthanides, in the top row, and the
Actinides in the bottom row.
Called Rare Earth Elements
Placed in periods 6 & 7 between the
alkaline earth metals and the transition
metals.
Lanthanides
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Soft, Malleable, shiny metals with high
conductivity.
Actinides
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Only thorium and Uranium exist on
Earth in any significant amounts.
Uranium is used to produce energy in
nuclear power plants.
All elements after Uranium on the table
were created artificially in a laboratory.
Bonding in Metals
Most have 1-3 valance electrons which they lose
easily.
Usually lose the electron to a nonmetal and form
ionic bonds.
Sometimes metallic bonding occurs – the positively
charged ions are surrounded by a sea of electrons.
The electrons can slide past each other . This is
how they are malleable, ductile, and good
conductors of electricity. Page 331.
For example, during the reaction of sodium with chlorine:
sodium
(on the left) loses its one
valence electron to chlorine
(on the right),
resulting in
a
positively charged sodium ion
(left) and a negatively charged
chlorine ion (right).
The reaction of sodium with chlorine
Concept simulation - Reenacts the reaction of sodium with chlorine.
(Flash required)
Metal Facts
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Aluminum most abundant metal in the Earth’s
crust.
Iron second most abundant. Metals must be
dug or mined from earth’s crust.
Iron is most widely used metal (steel), cobalt
is sometimes used in steel.
Nickel gives it the shiny color.
Nonmetals and Metalloids
Where are they located on the
periodic table?
What are the properties of
nonmetals and metalloids?
What is a Nonmetal?
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17 Nonmetals
located to the right
of the zig-zag line
on the periodic
table.
Physical properties
are the opposite of
metals.
Physical Properties
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Dull, brittle, low
densities, poor
conductors of heat and
electricity.
Many non metals are
gases at room
Temperature which
means they have low
boiling points.
Chemical Properties
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Most nonmetals form compounds. They
gain or share electrons.
Family – Group 18 do not. This is
because they have 8 valence electrons
in their outermost energy level.
Compounds of Nonmetals
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When nonmetals
and metals react the
valence electron
moves from the
metal to the
nonmetal.
Compounds of Nonmetals
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Nonmetals can also form compounds with
other nonmetals.
Atoms share electrons and become bonded
together.
Molecules that contain only 2 atoms are
called diatomic molecules. (oxygen, nitrogen,
hydrogen)
Attracting Electrons
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Most nonmetals
form both ionic and
covalent
compounds.
When a nonmetal
gains electrons from
metals the
nonmetals become
negative ions in
ionic compounds
Bonding with other nonmetals
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Atoms of nonmetals
share electrons to
form covalent
compounds.
NH3
Covalent Bond
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The idea of covalent bonding can be
traced to Gilbert N. Lewis, who in 1916
described the sharing of electron pairs
between atoms.
First Energy Level: 2
Second Energy Level: 8
Third Energy Level: 8
Atomic Structure
Families of Nonmetals
Group 18 is the only family that
consists of all nonmetals.
Carbon Family
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4 valence electrons
Carbon is the only nonmetal.
All living things contain compounds that
are made of carbon atoms.
Nitrogen Family
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Group 15 – 5 valence electrons
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Atmosphere is 80 % nitrogen.
Oxygen Family
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Group 16, 6 valence electrons.
Usually gain or share 2 valence
electrons.
Oxygen is a diatomic molecule
Oxygen is very reactive – it can
combine with nearly all elements.
Most abundant element in the Earth’s
crust, 2nd most abundant in the
atmosphere.
Halogen Family
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Group 17 contains fluorine, chlorine,
bromine, iodine, astatine.
7 valence electrons, gains or shares one
valence electrons when it reacts.
Noble Gases
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Group 18, do not mix with others.
Do not gain, share, lose electrons.
Chemically stable because they have a
full outer energy level.
Hydrogen
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Alone in the upper left corner.
Simplest element – usually its atoms
contain one proton and one electron.
Hydrogen is rarely found on Earth as an
element. Usually combined with
oxygen as water.
Metalloids
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On the border between metals and
nonmetals.
Have characteristics of metals and nonmetals
Most useful property is the varying ability to
conduct electricity..
Used to make semiconductors which are
substances that under some conditions can
carry electricity like a metal, while other
conditions cannot carry electricity like a
nonmetal. Used to make computer chips.