Transcript rare earth elements

Physical Science
Ch 5 Periodic Table
Standards
• Relate properties of atoms and their position in the
periodic table to the arrangement of their electrons.
• Differentiate among conductors, semiconductors, and
insulators.
• Describe how scientific inferences are drawn from
scientific observations & provide examples.
• Discuss effects of technology on environmental quality.
• Predict human impact on environmental systems .
• Weigh alternative strategies for solving specific societal
problems by comparing human, economic, and
environmental aspects.
Chapter assignments from the
book:
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139/26-28
140/1-8
150/107
155/1-8
164/1-4
Mendeleev
1. Placed elements in order by mass
2. Elements with similar properties were in
the same column
3. His periodic table could be used to
predict properties of newly discovered
elements
4. He predicted an unknown element would
have properties similar to aluminum and
called it eka-aluminum
• The Periodic Table of the Elements is a
way to arrange the elements to show a
large amount of information and
organization.
• The Periodic Table is NOW arranged in
order of increasing atomic number.
Periodic Table Organization
1. As you read across the chart from right
to left, a row of elements is a Period.
2. As you read down the chart from top to
bottom, a column of elements is a Group
or Family
3. Elements in a column have similar
properties
Group IA
alkali metals
Group IIA
alkaline earth
Metals
Group IIIB-IIB
transition metals
Inner Transition
Metals
Lanthanide Series - also called the rare earth elements.
Actinide Series
Group VIIIA
noble gases
or inert gases
Group VIIA halogens
Bright Green nonmetals
Purple metalloids or
semiconductors
Light Blue - other
metals
In the periodic table
• A set of properties repeats from row to row
• The atomic number increases from left to
right
• The atomic number is the number of
protons in an atom of an element
• The atomic number is equal to the number
of electrons when an atom is neutral
http://periodic.lanl.gov/default.htm
• Periodic Table of the elements
• Los Alamos
• Atomic Mass - the mass of one mole of an
atom. (One mole is 6.02 x 1023 atoms)
• Mass Number (the atomic mass number
rounded) - the total amount of protons and
neutrons in the nucleus of an atom
• Example: Tantalum, atomic # 73
• 180.948 is the atomic mass
• 181 is the p+n total
• Subtract 73 p and it has 108 neutrons
• Now you try with Zinc
• 65.39  65P+N - 30P = 35N
Electrons
• Are found in energy levels (or orbitals)
around the nucleus.
• The period an element is in indicates how
many energy levels in which an atom has
electrons (see long periodic chart given to
you)
• Ca has 2 8 8 2
• Al has 2 8 3
Energy Level
1
# of orbitals
1 (En. Lev.
Max # of e’s
2 (2 x # of
2
4
S
P
3
9
D
18
4
16
F
32
Squared)
orbitals)
8
Atomic Mass
• The weighted average of the masses of an
element’s isotopes found in nature.
• Atomic mass unit - one twelfth of the mass
of a carbon -12 atom (Carbon – 12 is the
Standard Mass)
• The unit is an amu (1/12 of the mass of C12.)
Reactivity Patterns
• Reactivity is closely related to the number of
VALENCE electrons in the atoms of an element.
– Most reactive metal group is IA with 1 valence e
– Most reactive nonmetal group is VIIA with 7 valence
e’s
• On the metal side of the Periodic Chart, going
down a group, the elements get more reactive.
Cs > Na
(This is determined by how they
behave when placed in water)
• On the nonmetal side, going up, the elements
get more reactive. F > At
Highly reactive
elements are
stored in
containers
containing oils
or argon
• Reactive metals EASILY lose valence
electrons (1 or 2 to have 8 in outer E level)
• Reactive nonmentals EASILY take
valence electrons (to have 8 in outer E
level.
More on Reactivity
• Examples:
• Ge would be a better electrical conductor
that Se (Ge more metallic than Se)
• Two highly reactive elements in Period 3
are the metal Na and the nonmetal Cl
Most metals are…
• Good conductors of heat and electricity
• Malleable
• Ductile
Most nonmetals are…
• Poor conductors of heat and electricity
• Brittle
Etc.
• Some highly reactive metals are stored in
argon
• Sodium is found in nature only in
compounds (highly reactive)
• Carbon is found in most compounds in
your body except water