Transcript The Periodic Table 2013

The Periodic Table
A. History of the Periodic Table
1. First developed by Dmitri
Mendeleev in 1869.
2. Mendeleev was looking
for a way to arrange the
elements.
3. As he studied properties
such as atomic mass, he
noticed a repeating
pattern.
Side Note: What does “Periodic”
mean??
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“Periodic” means “repeated in a pattern”!
HOWEVER, Mendeleev had to leave some spaces
because not all elements lined up according to atomic
mass. Notice that he used his information to PREDICT
masses. Very scientific……!
B. The Modern Periodic Table
1. c. 1914: Henry G.J.
Moseley realized that
elements could be
arranged according to
atomic NUMBER rather
than mass.
2. Seaborg (1944)
a. rearranged Periodic Table with...
 Lanthanide
and Actinide Series pulled
out/separated from main Periodic Table
b. discovered 10 new elements & countless
isotopes
B. Arrangement of the PT
16
1 2
14
13
15
18
17
1. The boxes are arranged
into vertical columns
called groups or families.
They are numbered 1 - 18.
a. The group numbers tell
us the number of electrons
in that element’s outer
energy level - the number
in red
b. valence electrons
electrons
found in the
outermost energy level
c. Octet Rule
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We just said that the “red number” in the
family/group number = the number of electrons in
the outer shell or valency.
Octet Rule: The tendency of atoms to gain or lose
electrons so they acquire eight electrons in their
outer energy level.
d. Groups to Know
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Group 1 - Alkali Metals
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Group 2 - Alkaline Earth
Metals
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Group 17 - Halogens
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Group 18 - Noble Gases
2. Periods
a. The boxes are arranged into horizontal rows called
periods.
b. The period numbers tell us the number of energy levels
that an atom has
c. Periods are numbered 1 through 7
1
2
3
4
5
6
7
3. Regions of the Periodic Table
a. Metals - to the left of the
stair-step line
b. Non-Metals - to the right
of the stair-step line
c. Metalloids - on the stairstep line
a. Metals
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Found to LEFT of zigzag line on table
Good conductors of heat & electricity
Malleable
Ductile
High melting points
Shiny
Tend to lose electrons
b. Nonmetals
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Found to RIGHT of zigzag line on table
Poor conductors of heat & electricity
Brittle when solid
Dull
Low melting points
Tend to gain electrons
c. Metalloids/Semi-Metals
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Found along both sides of zigzag line
Properties of both metals & nonmetals
Okay conductors of heat & electricity
Shiny or dull
C. Trends in the Periodic Table
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Valence number
Charge of ion (positive or negative)
Tendency to gain or lose electrons
Metallic vs. nonmetallic properties
Atomic size (radius)
Ionization energy
Electronegativity (which ones WANT electrons the most)
1. Across a Period
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radius decreases (size of atom gets smaller)
ionization energy increases
electronegativity increases
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b/c
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number of valence electrons increases…
 so EMF increases…
 so valence electrons held more tightly…
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2. Down a Family
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radius increases
ionization energy decreases
electronegativity decreases
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b/c
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number of energy levels increases…
so valence electrons held less tightly…