Transcript The Periodic Lawx

Chapter 5The Periodic Law
5.1-History of the Periodic Table
5.2-Electron Configuration & the Periodic Table
5.3-Electron Configuration & Periodic Properties
5.1-History of the
Periodic Table
Pages 123-127
Mendeleev
 Dmitri
Mendeleev (1869, Russian)
 Organized
elements
by increasing
atomic mass.
 Elements with
similar properties
were grouped
together.
 There were some
discrepancies.
Mendeleev
 Dmitri
Mendeleev (1869, Russian)
 Predicted
elements.
properties of undiscovered
Moseley
 Henry
Moseley (1913, British)
 Organized
number.
elements by increasing atomic
 Resolved
discrepancies in Mendeleev’s
arrangement.
 Periodic
Law-the physical and chemical
properties of the elements are periodic
functions of the atomic numbers.
Organization of the Elements

Periodic table-an arrangement of the
elements in order of their atomic numbers
so that elements with similar properties
fall in the same column, or group.
Additions to Mendeleev’s Periodic Table

Noble gases




Lanthanides



Group 18
Argon discovered in 1894
Took so long to discover because very unreactive
14 elements with atomic numbers from 58-71
Placed below the periodic table to conserve space
Actinides


14 elements with atomic numbers 90-103
Also placed below periodic table
5.2-Electron Configuration &
the Periodic Table
Pages 128-139
Periods & Blocks of the Periodic Table

Length of period (row) determined by how
many electrons can occupy the sublevels
being filled.



1st period-1s sublevel being filled with 2
electrons  2 elements, H & He
3rd period-3s & 3 p sublevels being filled with
2+6 electrons  8 elements
Periodic table is divided into “blocks”
based on the filling of sublevels with
electrons.
Blocks of the Periodic Table
Determining Period from Configuration
An element’s period can be determined by
looking at its electron configuration
 The highest occupied energy level
corresponds to the element’s period


As: [Ar]3d104s24p3

4 in 4p3 indicates that the highest energy level that
electrons occupy is the 4th. Therefore, As is located
in the 4th period of the periodic table.
Metallic Character
Metals
 Nonmetals
 Metalloids

Areas of the Periodic Table



Main Group Elements
Transition Metals
Inner Transition Metals
s-Block Elements: Groups 1 & 2
Chemically reactive metals
 Include the alkali metals and the alkaline
earth metals

Alkali metals
Group 1 metals
 ns1
 Silvery appearance and very soft
 Not found pure naturally because so
reactive
 Because of extreme reactivity with
moisture, usually stored under kerosene
 Video: Disposal of Surplus Sodium
 Video: Alkali Metals in Water

Alkaline-Earth metals
Group 2 metals
 ns2
 Harder, denser, & stronger than alkali
metals
 Also too reactive to be found free in
nature (but less reactive than Gp. 1)
 Video: Magnesium/silver nitrate mixture
reacting with water

d-Block Elements: Groups 3-12






Metals with typical metallic properties
Called “transition elements”
Typically less reactive than Gps. 1&2, & some are
extremely unreactive
d sublevels first appears at the 3rd energy level
Fills after 4s
Variations from expected in d-block, so elements
in the same group do not necessarily have the
same outer e- configuration
p-Block Elements: Groups 13-18
p and s-block elements together called
“main-group elements”
 Total number of electrons in highest
energy level=group # - 10



Group 17 elements have 17-10=7 outer
“valence” electrons
Properties of p-block elements vary
greatly since metals, nonmetals, and
metalloids are contained here
p-block Elements

Halogens
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Group 17 nonmetals
Most reactive nonmetals


React with most metals to form salts
Metalloids

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Fall on both sides of a “stair-step” line
separating metals and nonmetals
Semi-conductors
f-Block Elements:
Lanthanides & Actinides

Lanthanides


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
Top row of f-block
14 elements
Shiny metals similar in reactivity to the
alkaline-earth metals
Actinides




Bottom row of f-block
14 elements
All radioactive
1st 4 elements found naturally on Earth;
remainder only lab-made elements
5.3-Electron Configuration &
Periodic Properties
Pages 140-154
Remember the Periodic Law
 When
elements are arranged in order of
increasing atomic #, elements with similar
properties appear at regular intervals.
Atomic Radius (pm)
250
200
150
100
50
0
0
5
10
Atomic Number
15
20
Atomic Radius
½
the distance between the nuclei of
identical atoms that are bonded together
 Increases to the LEFT and DOWN
1
2
3
4
5
6
7
Atomic Radius
Atomic Radius (pm)
250
K
200
Na
Li
150
100
50
Ar
Ne
0
0
5
10
Atomic Number
15
20
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
Ionization Energy
 First
Ionization Energy-energy required to
remove one electron from a neutral atom
 Increases UP and to the RIGHT
1
2
3
4
5
6
7
Ionization Energy
 First
Ionization Energy
He
1st Ionization Energy (kJ)
2500
Ne
2000
Ar
1500
1000
500
Li
Na
K
0
0
5
10
Atomic Number
15
20
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-
Ionization Energy
 Successive
Ionization Energies
 Large
jump in I.E. occurs when a CORE e- is
removed.
 Mg
Core e-
1st I.E.
736 kJ
2nd I.E.
1,445 kJ
3rd I.E.
7,730 kJ
Ionization Energy
 Successive
Ionization Energies
 Large
jump in I.E. occurs when a CORE eis removed.
 Al
Core e-
1st I.E.
577 kJ
2nd I.E.
1,815 kJ
3rd I.E.
2,740 kJ
4th I.E.
11,600 kJ
Electron Affinity
 Energy
change that occurs when an electron
is acquired by a neutral atom
 Tends to become less negative (less energy
released) DOWN and to the LEFT
1
2
3
4
5
6
7
Ionic Radius
 Ionic


Radius
Cations (+)

lose e-

smaller
Anions (–)

gain e-

larger
© 2002 Prentice-Hall, Inc.
Electronegativity
A measure of the ability of an atom in a
chemical compound to attract electrons
 Most electronegative element is fluorine


1
2
3
4
5
6
7
Given arbitrary value of 4; all others relative
Examples
 Which
atom has the larger radius?
Be
or Ba
Ba
Ca
or Br
Ca
Examples
 Which
atom has the higher 1st I.E.?
N
or Bi
N
Ba
or Ne
Ne
Examples
 Which
has the greater electonegativity?
K
or Li
Li
Al
or Cl
Cl
Examples
 Which
particle has the larger radius?
S
or S2-
S2-
Al
or Al3+
Al