Download Increasing Radii

Periodic Law:
A periodic repetition of chemical and physical properties of
elements when the elements are arranged by increasing
atomic number.
For example:
Na behaves much like Li
Mg behaves much like Be
P behaves much like N
S behaves much like O
Cl behaves much like F
Ar behaves much like Ne
Na is the eighth element after Li
Mg is the eighth element after Be
P is the eighth element after N
S is the eighth element after O
Cl is the eighth element after F
Ar is the eighth element after Ne
Russian Chemist Dmitri Mendeleev is usually given credit for understanding
the implications of this repetition in properties and he arranged elements
based on similarities of properties.
Henry Moseley first arranged elements in order of increasing Atomic Number.
1
Mendeleev's Early Periodic Table, Published in
1872
Mendeleev is from Russia, but the chart is in German. Why?
2
Groups or Families: Vertical Columns in the periodic table
(Up and Down)
Periods: Horizontal Rows across the periodic table
(Side to Side)
Representative Elements: Groups 1-2 and 13-18 (the S and P blocks)
These groups generally display a wide range of properties
which are said to be representative of most elements.
Transition Elements: Groups 3-12 (the D block)
These elements gradually change (or transition) their properties
and are more similar to each other than to many elements in the
representative group.
3
Metals: elements that typically have the following properties
good conductors of heat and electricity
malleable-can be beaten into a flat sheet
ductile-can be drawn into a wire
usually shiny solids when clean and smooth
Metals are on the left side of the periodic table.
Non-Metals: elements that are not like metals
poor conductors of heat and electricity
brittle-break into pieces when hit or are gases
dull looking solids if not a gas
Non-metals are on the right side of the periodic table.
Metalloids: elements that have properties of both metals
and non-metals (these are also called semiconductors)
B, Si, Ge, As, Sb, Te
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1
2
3
4
5
6
7
Non-metals
Metals
Metaloids
Notice that Hydrogen is considered to be a non-metal even though it is placed with
the group 1 metals. Hydrogen does form positive ions like the metals do.
5
Specially Named Groups or Families
Alkali Metals:
Group 1 metals, all have s1 electron configuration
Very reactive metals-form ions with positive one charge (+1)
Alkaline Earth Metals:
Group 2 metals, all have s2 electron configuration
Reactive metals-form ions with positive two charge (+2)
Halogens:
Group 7 nonmetals, all have s2, p5 electron configuration
Very reactive nonmetals-form ions with negative one charge (-1)
when reacting with metals
Noble Gases:
Group nonmetals, all have s2, p6 electron configuration (except He)
Nonreactive elements-almost no know compounds containing these
elements. Remember that a full energy level is not reactive.
6
Color coding the groups on a periodic table may help you to
remember where the named groups and series are.
1
2
3
4
5
6
7
Lanthanides
Series
Actinides
Alkali Metals
Halogens
Alkaline Earth Metals
Nobel Gases
Transition Metals
Groups
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Periodic Table Labeling Activity (Using your book, notes, or collaboration with others)
1
2
3
Obtain a “fresh” periodic table
Obtain a set of colored pencils
Shade in appropriate areas of the periodic table (using different colors) that correspond to the
following sections of the periodic table:
Alkali Metals; Alkaline Earth Metals; Halogen; Noble Gases
Transition Metals; Metalloids
4
Create a color-coded key that clearly indicates which color corresponds to which section of the
periodic table.
Bonus Work: Review/Tie-in with Chapter 4 material (Begin in class, finish at home)
1
2
3
4
5
Using another fresh periodic table, create a similar color-coded key that shows the location of atoms
that have each of the following designations:
“s” block; “p” block; “d” block; “f” block
Within each block label each column as 1, 2, 3 ….. (for example which column would be s1, p3, d6,
or f2).
Choose an element within each block and write out an electron configuration for that element (use
the noble gas shortcut method).
Choose an element from each s or p column and write a dot diagram for that element.
For each element for which you drew a dot diagram, identify two other elements that would have the
same number of dots in their dot diagrams (do not draw the dot diagrams, just list the element
symbols)
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1
2
3
4
5
6
7
Gases
Liquids
Solids
Diatomic Elements
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Ion Formation
+11
+9
F
Na
11 protons, 11 electrons
Zero charge
Na
+1
+11
11 protons, 10 electrons
+1 charge
9 protons, 9 electrons
Zero charge
+9
F -1
9 protons, 10 electrons
-1 charge
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Periodic Trends:
Many properties of the elements change in a regular way as
you move either up and down or left and right on the
periodic table.
Atomic Radius: half the distance between the nuclei in a molecule
consisting of identical atoms
Ionic Radius: radius of an ion (an atom that has become charged)
Ionization Energy: the energy required to remove an electron from
a gaseous atom
Electronegativity: a measure of the ability of an atom to attract
electrons that are in a chemical bond
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Atomic Radius: half the distance between the nuclei in a molecule
consisting of identical atoms
Since atoms do not actually have an edge, we define the radius based on one half
the distance between two nuclei in a compound.
As you move from left to right across a period, what happens to the radius of
the elements?
As you move from top to bottom in a group, what happens to the radius of the
elements?
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Increasing Radii
Period Trend
Increasing Radii
Group
Trend
Overall Trend
Atomic Radii in picometers (pm)
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1
2
3
4
5
6
7
Increasing Atomic Radius Arrows
Summary Arrow for Increasing Atomic Radius
You need to remember that atoms get larger when you move from the right
to the left or from top to bottom on the periodic table!
This trend is related to several other trends that follow.
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Trends in Ionization Energies (kJ/mol) for the Representative Elements
The trend can be hard to see in this form.
15
The same data plotted in a different way. Wow! What a complicated graph!
We need to make sense of this information!
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If we look at data from a single period (across), we get this graph.
Ionization energy (kJ/mol)
Ionization Energy for Period 2
2500
2000
1500
1000
500
0
Li
Be
Be
C
N
O
F
Ne
Atomic Number or Element
In general, ionization energy increases as you move from left to
right across each period.
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If we look at data from a single group (vertical), we get this graph.
Ionization energy (kJ/mol)
Ionization Energy for Nobel Gases
2500
2000
1500
1000
500
0
He
Ne
Ar
Kr
Xe
Rn
Atomic Number or Element
Ionization energy decreases as you move from top to bottom in a group or family.
Or, Ionization energy increases as you move from bottom to top in a group or family.
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1
2
3
4
5
6
7
Increasing Ionization Energy Arrows
Summary Arrow for Increasing Ionization Energy
This is exactly opposite the trend for atomic size!!! Said another way, small
atoms hold onto their outer shell electrons more tightly than larger atoms do.
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Electronegativity
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1
2
F
3
4
5
6
7
Increasing Electronegativity Arrows
Summary Arrow for Increasing Electronegativity
Note: Nobel gases do not form compounds, so they have no electronegativity
values.
This trend is the same as ionization energy which makes sense because atoms
with high electronegativity tend to hold onto their electrons firmly.
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Increasing Radii
Positive Ions
Negative Ions
Increasing Radii
Increasing Radii
Ionic Radii in picometers
Notice that the negative ions are larger than all but the very largest positive ion.
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Shielding: Inner shell electrons “blocking” the pull of the
nucleus for the outer shell electrons.
The stronger the shielding, the larger the atom becomes. The outer shell
electrons do not feel the pull of the nucleus as much if they are strongly
shielded.
The weaker the shielding, the smaller the atom becomes. The outer shell
electrons feel the pull of the nucleus more strongly if they are weakly
shielded.
Increasing the positive charge in the nucleus increases the pull of the
nucleus for the all electrons.
If the number of outer shell electrons increases while the number of inner
shell electrons remains constant, the shielding is decreasing which causes the
atoms to be smaller. This is what happens as we move from left to right
across a period.
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Strongest
Shielding
+3
Li
Look at a series of atoms to see how shielding works?
+4
Be
+7
+5
+6
+9ininNucleus
NucleusPulling
Pullingon
on22inner
innershell
shelland
and54362one
7outer
outer
shell
shell
+3
+4
outer
+8
electrons-like
electrons-like
22blockers
blockers
and
and54326and
7receivers
receivers
shell
electron-like
2 blockers
one receiver
+10 in Nucleus Pulling on 2 inner shell and 8 outer
shell electrons- like 2 blockers and 8 receivers
More receivers with the same number of blockers
is weaker shielding which means that the electrons
will feel more pull from the nucleus-smaller atom.
Weakest
Shielding
+5
B
+6
C
+7
N
+8
O
+9
F
+10
Ne
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When a shell becomes full, the next electron must go into a
higher energy level. Higher energy means farther from the
nucleus, so the new shells are larger than the previous shells.
Going down a group, each element has the same type of
electron in its outer shell, but the electron is in the next higher
energy level.
Therefore, going down a group makes the atoms larger even
though there are more protons in the nuclei as you go down a
group.
Larger numbers of electrons in inner shells also increase
shielding as you move down a group-increased shielding means
larger atoms.
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+3
Increasing Shielding
Li
2 shells present-2 inner shell
electrons and 1 outer
+11
Na
3 shells present-10 inner shell
electrons and 1 outer
Largest Atom
Ne
+10
Smallest
Atom
2 shells present-2 inner shell
electrons and 8 outer
Ar
+18
3 shells present-10 inner shell
electrons and 8 outer
Increasing Shielding
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A positive ion will be smaller than the atom that created it
because there will be more protons than electrons in the ion.
The electrons will be pulled more strongly by the nucleus.
A negative ion will be larger than the atom that created
because there will be more electrons than protons in the ion.
The greater the charge of the ion, the more pronounced the size
change will be. For example, a +3 ion will be smaller than a
+2 or +1 ion in the same period and a -3 ion will be larger than
a -2 or -1 ion in the same period.
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+11
+9
F
Na
11 protons, 11 electrons
Zero charge
Na
+1
+11
11 protons, 10 electrons
+1 charge
9 protons, 9 electrons
Zero charge
+9
F -1
9 protons, 10 electrons
-1 charge
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Ionization energy depends upon how close the electron is to the
nucleus-the closer the electron, the higher the ionization energy.
Smaller atoms have higher ionization energies!
Larger atoms have lower ionization energies!
Ionization energy will have a trend opposite to atomic radius.
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Note: a very large increase in ionization energy occurs when ionization
would be removing what was previously an “inner shell” electron.
1st
Na+ 1s2, 2s2, 2p6
4th
Si+4 1s2, 2s2, 2p6
2nd
Mg+2 1s2, 2s2, 2p6
5th
P+5 1s2, 2s2, 2p6
3rd
Al+3 1s2, 2s2, 2p6
6th
S+6 1s2, 2s2, 2p6
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An atom that attracts its outer shell electrons strongly will have a
high electronegativity. Within a period, atoms are smaller to the
right because the nucleus attracts the outer shell electrons
strongly because of increased nuclear charge and decreased
shielding.
Therefore electronegativity will have a trend opposite to atomic
radius.
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1
2
3
4
5
6
7
Increasing Ionization Energy Arrows
Summary Arrow for Increasing Ionization Energy
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1
2
3
4
5
6
7
Increasing Electronegativity Arrows
Summary Arrow for Increasing Electronegativity
Note: Nobel gases do not form compounds, so they have
no electronegativity values.
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Key Skills for chapter 5:
1) Based on an element’s position on the periodic table, you need to be able to
identify: the name of the family or group, the period, the general classification
(metal, non-metal, or metalloid), and what larger group it belongs to
(representative, transition, inner transition, etc…).
2) Based on the identity of an element, you also need to be able to identify
whether it is a solid, liquid, or gas, and whether it is a diatomic element or not.
3) When given two or more elements you need to be able to correctly arrange
them in order of increasing: atomic size (radii), electronegativity, and ionization
energy.
4) When given a representative element, you need to be able to predict what type
of ion the element will form. Type includes both the sign of the charge (+ or -)
and the amount of charge (1, 2, or 3 etc…).
5) When given two or more ions you need to be able to correctly arrange them in
order of increasing size.
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Practice
1
2
3
4
5
6
7
35
Which of the following atoms should have the smallest atomic radius?
A) O
element 8
B)
Be
element 4
C)
C
element 6
D) Li
element 3
36
Which of the following atoms should have the largest atomic radius?
A) Sr
element 38
B)
Be
element 4
C)
Ca
element 20
D) Ba
element 56
37
Which of the following atoms should have the highest electronegativity?
A) Cl
element 17
B)
Na
element 11
C)
Si element 14
D) Ar
element 18
38
Which of the following atoms should have the lowest electronegativity?
A) S
element 16
B)
Te
element 52
C)
O
element 8
D) Po
element 84
39
Which of the following atoms should have the lowest ionization energy?
A) Li
element 3
B)
K
element 19
C)
Na
element 11
D) Cs element 55
40
Which of the following atoms should have the highest ionization energy?
A) Rb element 37
B)
Zn
C)
S
D) V
element 30
element 16
element 23
41
Which of the following atoms is an alkali metal?
A) Rb
element 37
B)
Zn
element 30
C)
Mg
element 12
D) Al element 13
42
Which of the following atoms is a halogen?
A) Br element 35
B)
Si element 14
C)
Ca
D) Ne
element 20
element 10
43
Which of the following atoms is a noble gas?
A) N
element 7
B)
H
element 1
C)
Kr
element 36
D) Be element 4
44
Which of the following atoms is an alkaline earth metal?
A) Ni element 28
B)
K
element 19
C)
Cl
element 17
D) Ca element 20
45
Which of the following atoms is metalloid?
A) Al element 13
B)
K element 19
C)
P element 15
D) Ge element 32
46
Which of the following atoms would form a +1 ion when it becomes an ion?
A) Al element 13
B)
K
element 19
C)
F
element 9
D) Ne element 10
47
Which of the following atoms would form a -1 ion when it becomes an ion?
A) O element 8
B)
Li element 3
C) Br element 35
D) Mg element 12
48
Which of the following atoms would be least likely to form an ion?
A) S element 16
B)
He
element 2
C)
Cs
element 55
D) Cl element 17
49
Which of the following ions would be the smallest?
A) S-2
element 16
B)
Na+1
element 11
C)
Mg+2
element 12
D) Cl-1
element 17
50
Which of the following ions would be the largest?
A) S-2
element 16
B)
Na+1
element 11
C)
Mg+2
element 12
D) Cl-1
element 17
51
Which of the following ions would have the same electron configuration as argon
(element 18)?
A) Br-1
element 35
B)
K+1
element 19
C)
Mg+2
element 12
D) Ar+1
element 18
52
Which of the following atoms is a transition metal?
A) Sr element 38
B)
Cu element 29
C)
Xe element 54
D) Li element 3
53
Which of the following atoms is correctly called a diatomic element?
A) S element 16
B)
Be element 4
C)
He element 2
D) N element 7
54