I II III
III. Periodic Trends
(p. 140 - 154)
Ch. 6 - The Periodic Table
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A. Periodic Law
When elements are arranged in order of
increasing atomic #, elements with similar
properties appear at regular intervals. Each
interval corresponds to a family.
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Atomic Number
A. Know 6 Trends for TEST
M R E I R O increasing trends
Metallic Character: loosely held electrons
Radius (size of atom)
Electron Affinity (electronegativity)
Ionization Energy (first ionization E only)
Reactivity (bonding) of Metals losing e- or
Nonmetals gaining e-
Oxidation State (ionic charge)
A. Periodic Trends described
Most trends of chemical properties on the periodic table can be explained
by
Radius (size) of atom: effects the nuclear attraction, the
electromagnetic attraction of positive nucleus and negative electrons
Octet Rule: all atoms want to achieve 8 valence electrons, a stable noble
gas configuration and so will react (bond) in ways to do that
Metals will lose electrons to do this and Nonmetals will gain electrons
Metals = loosely held electrons causing properties like being malleable, ductile, luster, and good conductors of electricity and heat
Nonmetals = tightly held electrons making them be brittle, dull, and insulators (bad conductors)
Metalloids = have properties of both in different circumstances
B. Metallic Character M
M
Atomic Radius (size of atom) as # of shells increase the size gets bigger and the nuclear attraction (+ nucleus for –
electrons) for the valence electrons is decreased
© 1998 LOGAL
C. Radius R
Atomic Radius
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C. Atomic Radius
Li
ArNe
KNa
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2
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4 5
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7
Atomic Radius Increases to the LEFT and DOWN
C. Atomic Radius
Why larger atoms going down? Higher energy levels have larger shells further from nucleus
Shielding - core e- block the attraction between the nucleus and the valence e- alonging valence electrons to be lost more easily
Why smaller to the right? Increased nuclear charge within the same shell, without
additional shielding, pulls e- in tighter
C. Atomic Radius
Ionic Radius of
Cations (+)lose e- and become
smaller due to less
shells
Anions (–)gain e- and stay
about the same
size
C. Radius changes as neutral atoms become ions
Measure of the tendency to gain electrons (also called electronegativity)
Electron affinity is low for metals so easy to remove e-
Electron affinity is high for nonmetals due to smaller size and need a just a few more e- to reach the stable octet
D. Electron Affinity E
The Pauli Scale measures electronegativity on a scale of 0 to maximum of 4
D. Also called Electronegativity E
1
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4 5
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7
Increases UP and to the RIGHT
E. Electron Affinity
X
X
X
X
X
X
F
This is the amount of energy required to remove the first outer electron Ionization energy is low for metals so easy to remove electrons
Ionization is high for nonmetals and especially the noble gases because electrons are held tightly
E. Ionization Energy I
First Ionization Energy
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E. Ionization Energy
KNaLi
Ar
NeHe
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4 5
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First Ionization Energy Increases UP and to the RIGHT
E. Ionization Energy
Why opposite of atomic radius?
In small atoms, e- are close to the nucleus where the attraction is stronger
Why higher near the noble gases?
Stable e- configurations (or very close to 8 valence e-) don’t want to lose e-
E. Ionization Energy
Successive Ionization Energies
Mg 1st I.E. 736 kJ
2nd I.E. 1,445 kJ
Core e- 3rd I.E. 7,730 kJ
Large jump in I.E. occurs when a CORE e- is removed.
E. Ionization Energy
Al 1st I.E. 577 kJ
2nd I.E. 1,815 kJ
3rd I.E. 2,740 kJ
Core e- 4th I.E. 11,600 kJ
Successive Ionization Energies
Large jump in I.E. occurs when a CORE e- is removed.
E. Ionization Energy
F. Chemical Reactivity R
Alkali Metals = most reactive metals, explosive with water Alkaline Earth Metals = also reactive Transition Metals = less reactive Halogens = most reactive nonmetals Noble Gases = inert, nonreactive
X
X
X
X
X
X
G. Oxidation State O
+3 +/- 4 -3 -2 -1
Families IA to VIIIA correspond to having that number of valence
electrons (remember all want 8 valence e)
Charges are positive when valence electrons are lost; Charges are
negative when valence e-’s are gained+1 +2
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4 5
6
7
This is the general trend but…transition metals can have a range of charges from +1 to +7
G. Oxidation State
+ -
C
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2
3
4 5
6
7
Melting/Boiling Point Highest in the middle of a period.
H. Melting/Boiling Point
Which atom has the larger radius?
Be or Ba
Ca or Br
Ba
Ca
Examples
Which atom has the higher 1st I.E.?
N or Bi
Ba or Ne
N
Ne
Examples
Which atom can have an oxidation state of +1?
Li or C
S or Kr
Li
S
Examples
Which atom can have an oxidation state of -2?
Which particle has the larger radius?
S or S2-
Al or Al3+
S2-
Al
Examples