iiiiii iii. periodic trends (p. 140 - 154) ch. 5 - the periodic table
TRANSCRIPT
I II III
III. Periodic Trends(p. 140 - 154)
Ch. 5 - 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.
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B. Chemical Reactivity
Families Similar valence e- within a group result in
similar chemical properties
B. Chemical Reactivity
Alkali MetalsAlkaline Earth MetalsTransition MetalsHalogensNoble Gases
Atomic Radius size of atom: ½ distance
between nuclei of identicalatoms bonded tog.
© 1998 LOGAL
First Ionization Energy
Energy required to remove one e- from a neutral atom.
© 1998 LOGAL
C. Other Properties
Atomic Radius
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D. Atomic Radius
Li
ArNe
KNa
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Atomic Radius Increases to the LEFT and DOWN
D. Atomic Radius
Why larger going down?
Higher energy levels have larger orbitals
Shielding - core e- block the attraction between the nucleus and the valence e-
Why smaller to the right?
Increased nuclear charge without additional shielding pulls e- in tighter
D. Atomic Radius
First Ionization Energy
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0 5 10 15 20Atomic Number
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E. Ionization Energy
KNaLi
ArNeHe ion: atom or
group of atomswith a (+) or (-) charge
ionization: any process that results in theformation of an ion
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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 small jumps within each group?
Stable e- configurations 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
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Melting/Boiling Point Highest in the middle of a period.
F. Melting/Boiling Point
Ionic Radius
Cations (+)
lose e-
smaller
© 2002 Prentice-Hall, Inc.
Anions (–)
gain e-
larger
G. Ionic Radius
H. ELECTRON AFFINITY
electron affinity: (def) energy change that occurs when an electron is acquired by a neutral atom
A + e- A- + energy Energy released: negative value
Energy gained: positive value
H. ELECTRON AFFINITY
Trends: Among elements of each period, the
halogens gain electrons most readily.
(analogy of buying & selling)
As a general rule, electrons are added with more difficulty down a group.
H. ELECTRON AFFINITY
Adding Electrons to Negative Ions
It is always more difficult to add a 2nd electron to an already charged ion.
This makes all 2nd electron affinity values positive.
I. ELECTRONEGATIVITY
electronegativity: (def) a measure of the ability of an atom in a chemical compound (bonding) to attract electrons
TRENDS: Across a period, tend to increase
Down a group, tend to decrease or stay the same
J. VALENCE ELECTRONS
valence electrons: (def) electrons available to be lost, gained, or shared in the formation of chemical compounds
Which particle has the larger radius?
S or S2-
Al or Al3+
S2-
Al
Examples
Which atom has the higher 1st I.E.?
N or Bi
Ba or Ne
N
Ne
Examples
Which atom has the larger radius?
Be or Ba
Ca or Br
Ba
Ca
Examples
Which atom has the higher melting/boiling point?
Li or C
Cr or Kr
C
Cr
Examples
REVIEW QUESTION
Which of the following is the most reactive metal?
Neon, Boron, Beryllium, Lithium, Silicon
Lithium
REVIEW QUESTION
The element in period 3 with the largest atomic radius is:
Sodium, chlorine, magnesium, argon
Sodium
REVIEW QUESTION
Which of the following elements is most electronegative?
Phosphorus, Carbon, Chlorine, Boron, Iodine
Chlorine
REVIEW QUESTIONS
Which of the following has the most metallic character?
Fluorine, chlorine, Bromine, Iodine
Iodine
REVIEW QUESTIONS
Which ionization energy (1st, 2nd, 3rd, etc) will show a jump in value for an atom of Be?
3rd ionization energy
REVIEW QUESTIONS
Which electron affinity value will be more negative: for F or N?
F – most negative values (will spend the most money)
All second electron affinity values are: positive or negative?
positive