Transcript The Periodic Table

The Periodic Table
Chapter 5
5.1 The periodic table
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Dimitri Mendeleev - publish first real periodic table 1869
 Based on chemical and physical properties
 Listed elements in increasing atomic mass order
 Left spaces for undiscovered elements
 His basic rule: the elements in any group, of the
table are similar to their column-mates. Ex, look at
the first column on the left, underneath hydrogen (H).
The elements in this group are the alkali metals;
they're all soft metals that react violently with water to
make hydrogen gas.
…… Periodic Table
atomic mass
density
melting point
oxide formula
aluminum
68
5.9
low
Al2O3
Ga(1875)
69.7
5.9
29.8 Co
Ga2O3
….. Periodic Table
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Mendeleev formulated the original Periodic Law Properties of elements are a periodic function of their atomic
mass.
1911 - Mosely (English) discovers the proton so....new
Periodic Law - Properties of elements are a periodic function
of atomic number.
*** History lesson - After his brilliant discovery, Mosely was
drafted into the infantry to fight for the crown in WW I. He
was killed. Only after the war was it realized that scientists
should probably not be drafted into combat roles. That policy
exists to this day.***
5.2 Electron configurations and the
periodic table
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*** valence e- have largest
effect on chemical/physical
properties
Label the groups/ families and
periods
s
s
s s
p p p p p p
s s
p p p p p p
s s d d d d d d d d d d p p p p p p
s s d d d d d d d d d d p p p p p p
s s d d d d d d d d d d p p p p p p
s s
f f f f f f f f f f f f f f
f f f f f f f f f f f f f f
Names of Families
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Group 1 - Alkali Metals –
They are not found alone in nature - why? explosive with
water - they are stored under kerosene - very reactive.
They react with nonmetals to form salts.
They are silvery, shiny (luster), have a low melting point, and
are soft (so soft, you can cut them with a knife).
They are malleable (able to flattened into a sheet) and ductile
(able to be drawn into a wire).
Sodium and Potassium are particularly important in body
chemistry.
…..Families
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Group 2 - Alkaline Earth Metals 2nd most reactive elements. Also not “lone
state” elements.
Harder, denser than group 1. Common in
sea salts.
…..Families
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Transition Metals - Groups 3-12.
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Harder, more brittle, higher melting point than groups 1 and 2.
Form colored compounds.
Conduct heat and electricity well and are shiny.
Pd, Pt, Au - very unreactive (Noble metals).
They can't be divided neatly into groups; all of them have very
similar properties.
Their valence electrons vary in chemical reactions. E.x. Iron (Fe),
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sometimes likes to give away 2e-, and sometimes 3e-.
…..Families
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Metalloids –
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B, Si, As, Te, At, Ge, Sb - stairs and 2 people under the
stairs.
Properties of metals and nonmetals.
Brittle - used in semiconductors, computers.
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….. Families
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Halogens - Group VII / 17 –
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most reactive of the nonmetals.
Not found free in nature.
Solids, liquids, and gases in this group.
Widespread - sea salts, minerals, living tissue.
Many applications - bleach, photography, plastics,
insecticides.
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….. Families
Group 18 –
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Noble Gases -
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Least reactive elements - used in air conditioners,
double pane windows, lights, balloons.
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….. Families
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Lanthanides - f block
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rare earth elements (not really rare) - shiny, silver,
reactive, make TV’s glow.
Some have very interesting properties. For example,
gadolinium (Gd) is the only rare earth that's
ferromagnetic--that is, it sticks to magnets, the way iron
does.
Lanthanum is the only superconductor among them; at
very low temperatures, it loses all resistance to the flow
of electricity.
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….. Families
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Actinides - f block
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unstable, radioactive - all but 4 are artificially
created.
Side note 
f block elements are called inner transition
elements - they were put into their current
position by Glenn Seaborg - the only living
person ever to have an element named after him.
5.3 Electron Configuration and
Periodic Properties
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Periodic Trends:
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For all of the following periodic trends you
should:
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know the definition
be able to draw the trend on periodic table
drawings with arrows
explain why the trend happens
relate the trend to other trends
apply the trends on an “AB” sheet
Periodic Trends
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1. Atomic Radius - basic idea is “how big an atom is”
- atoms are not spheres with outer boundaries due to
the wave mechanical model.
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2 trends
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size
size
- natural, logical - add more shells
- not logical! why?
 from left to right - more protons are added, but not
more shells. Higher charged nucleus pulls
electrons closer.
Periodic Trends
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Atomic Radius
BIGGER
Periodic Trends
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Atomic Radius
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Examples
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Which has a larger radius?
 Mg or Ca?
 F or B?
Periodic Trends
2. Electronegativity- basic idea - the
ability of an atom to attract electrons (Linus
Pauling)
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Electronegativity is related to atomic size…. They
are opposites
Larger
Trend
Larger
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Periodic Trends
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Electronegativity
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Examples
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Which has a larger electronegativity?
 Cs or Mg?
 Mn or F?
Periodic Trends
3. Ionization energy - energy required to remove the
most loosely held electron from the outer energy level
of an atom.
A(g)
+
energy
yields
Trend:
Larger
Larger
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A+(g) + e-
Periodic Trends
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IE is related to atomic radius - 2 reasons why smaller going down
the table
1. greater distance from the nucleus - less attraction
2. inner electrons “shield” outer electrons from the nucleus
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Examples
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Which has a higher IE
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Se or Cl?
B or Sr?
Periodic Trends
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Ionization Energy Cont’d
 There is also a 2nd and 3rd IE - always higher than the first. IE
of elements greatly increases when the outer shell has been
emptied.
 Example
 Which has a higher 2nd IE, Na or Mg? Which has a higher
3rd IE - Al or Mg?
Mg
Na
Periodic Trends
4. Electron Affinity - energy absorbed when an electron is
acquired by a neutral atom.
 Basic idea - some atoms want to take on electrons - they
have a high electron affinity value - they receive a lot of
energy when accepting electrons
 Trend:
Larger
Larger
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Periodic Trend
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Electron Affinity Cont’d
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Examples
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F or Na?
 F = -322 kJ/mole
Na = -53 kJ/mole
 F has a higher electron affinity - higher, more negative
value
Periodic Trends
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5. Valence electrons - outer shell electrons involved with
bonding –tells you about an element’s chemical behavior
+
Sodium
Chlorine
Salt
Periodic Trends
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6. Ionic Radius - the size of an ion.
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Ions are created by gaining or losing electrons.
Cation - positive, lost electrons
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Anion - negative, gained electrons
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Nonmetals tend to become anions
Cations are smaller than the neutral atom - why?
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Metals tend to become cations
they lost a shell
Anions are larger - why?
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more electron repulsion so shells are
pushed farther apart
Periodic Trends
Ionic Radius Cont’d
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Trend
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Example
Larger
Larger
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Li+1 or Be+2 - Li is bigger because less protons pull the
shell in less
O -2 or N -3 - N is bigger because less protons pull
the shell in less
Periodic Trends
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7. Activity (Reactivity)
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metals - larger atoms are more active - why?
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they lose electrons more easily
nonmetals - smaller more active - why?
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they gain electrons more easily
Periodic Table
Reactivity
 Trends
Larger
Metals
Larger
Larger
Larger
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Nonmetals
Most active metals + most active nonmetals = most stable compounds
ex: RbF - very stable
LiBr - less stable
Periodic Trends
8. Metallic character - some metals are said to be more
metallic than others - really it is just a statement about their
activity. If they are more active, they are said to be more
metallic.
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Trend
Larger
Larger
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Which is more metallic?
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Ca or Na?