Trends in the Periodic Table
Periodic Trends
In this chapter, we will rationalize
observed trends in
Sizes of atoms and ions.
Ionization energy.
Electron affinity.
Why is the Periodic Table
important to me?
 The periodic table is
the most useful tool to
a chemist.
 You get to use it on
every test.
 It organizes lots of
information about all
the known elements.
PERIODIC LAW
When elements are arranged in order of increasing atom
number, their physical and chemical properties show a periodic
pattern
HISTORY OF FORMATION OF PERIODIC
TABLE
ANTOINE LAVOISIER
Late 1790’s
French Chemist
Compiled a list of 23 known elements.
Many of the elements were known to exist
since prehistoric times (including Au, Ag,
C, O)
HISTORY OF FORMATION OF
PERIODIC TABLE
By mid-1800’s the known elements was
approximately 70.
The discovery of electricity,
spectrometer, and the onset of the
industrial revolution led to this explosion
in the number of elements.
HISTORY OF FORMATION OF
PERIODIC TABLE
DMITRI MENDELEEV
1869
Russian Chemist
First real periodic table
Combined both Doberiener and Newlands
Dmitri Mendeleev: Father of the
Table
HOW HIS WORKED…
 Put elements in rows
by increasing atomic
weight.
 Put elements in
columns by the way
they reacted.
SOME PROBLEMS…
 He left blank spaces for
what he said were
undiscovered elements.
(Turned out he was
right!)
 He broke the pattern of
increasing atomic
weight to keep similar
reacting elements
together.
Medeleev’s Table
The Current Periodic Table
Mendeleev wasn’t too far off.
Now the elements are put in rows by
increasing ATOMIC
NUMBER!!
The horizontal rows are called periods and
are labeled from 1 to 7.
The vertical columns are called groups are
labeled from 1 to 18.
Families on the Periodic Table
 Columns are also grouped
into families.
 Families may be one
column, or several columns
put together.
 Families have names rather
than numbers. (Just like
your family has a common
last name.)
Hydrogen
 Hydrogen belongs to a
family of its own.
 Hydrogen is a diatomic,
reactive gas.
 Hydrogen was involved in
the explosion of the
Hindenberg.
 Hydrogen is promising as
an alternative fuel source
for automobiles
Groups of Elements
1
1
1
2
3
Be
3
4
K
7
Oxygen group or Chalcogen
Transition metals
17
Halogens
13
Boron group
18
Noble gases
14
Carbon group
3
5
V
14
C
15
N
16
O
5
6
7
8
9
10
Al
Si
P
S
Cl
Ar
22
Rb Sr
Y
Zr Nb Mo Tc Ru Rh Pd Ag Cd
In
39
40
41
42
49
Hf
Ta
W
72
73
74
Cs Ba
55
56
Fr
Ra
87
88
*
W
25
43
26
44
Re Os
75
76
27
28
29
47
30
45
46
Ir
Pt Au Hg
Tl
77
78
81
79
48
31
80
32
33
34
Sn Sb Te
50
51
Pb Bi
82
83
52
Kr
35
36
I
Xe
53
54
Po At Rn
84
85
86
105
106
107
108
109
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
57
W
24
18
Rf Db Sg Bh Hs Mt
104
*
17 2
F Ne
8
6
7
9 10 11 12 13 14 15 16 17
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br
21
38
23
13
B
Hydrogen
Inner transition metals
4
Ca Sc Ti
12
18
He
20
37
6
16
Na Mg
19
5
Alkali earth metals
2
Li
11
4
Nitrogen group
2
H
1
15
Alkali metals
58
59
Ac Th Pa
89
90
91
60
U
92
61
62
63
64
65
66
Np Pu Am Cm Bk Cf
93
94
95
96
97
98
67
68
69
70
71
Es Fm Md No Lr
99
100
101
102
103
Groups of Elements
1
18
H
1
He
2
13
14
15
16
17
2
Li
Be
N
O
F
Ne
3
4
7
8
9
10
Na
Mg
P
S
Cl
Ar
11
12
15
16
17
18
K
Ca
As
Se
Br
Kr
19
20
33
34
35
36
Rb
Sr
Sb
Te
I
Xe
37
38
51
52
53
54
Cs
Ba
Bi
Po
At
Rn
55
56
83
84
85
86
Fr
Ra
87
88
1
Alkali metals
16
Oxygen family or Chalocogen
2
Alkaline earth metals
17
Halogens
18
Noble gases
15
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 367
Nitrogen family
Alkaline Earth Metals
 Second column on the
periodic table. (Group
2)
 Reactive metals that
are always combined
with nonmetals in
nature.
 Several of these
elements are important
mineral nutrients (such
as Mg and Ca
GROUPS OF ELEMENTS IN
PERIODIC TABLE
METALS
Vast majority of elements are metals.
Elements found to the left of the heavy
black line on periodic table.
Properties that most metals exhibit:
GROUPS OF ELEMENTS IN
PERIODIC TABLE
METALS (cont.)
Physical Properties:
Appearance – high luster
Tapping – malleable
Conductivity – conductor of heat and
electricity
GROUPS OF ELEMENTS IN
PERIODIC TABLE
METALS (cont.)
Chemical Properties:
Tend to form positive ions
In HCl – gas produced; corrosion
In CuCl2 - corrosion
Metallic Trends in Periodic Table
metallic character increases
nonmetallic character increases
metallic character increases
nonmetallic character increases
Transition Metals
 Elements in groups 312
 Less reactive harder
metals
 Includes metals used in
jewelry and
construction.
 Metals used “as metal.”
TRENDS IN PERIODIC TABLE
ATOMIC RADII
Definition - distance from nucleus to outer
edge of electron cloud of atom
Trend from left to right – decreases
Rationale – increasing nuclear charge
Trend from top to bottom – increases
Rationale – increasing energy levels
Carbon Family
 Elements in group 14
 Contains elements
important to life and
computers.
 Carbon is the basis
for an entire branch
of chemistry.
 Silicon and
Germanium are
important
semiconductors.
Nitrogen Family
 Elements in group 15
 Nitrogen makes up
over ¾ of the
atmosphere.
 Nitrogen and
phosphorus are both
important in living
things.
 Most of the world’s
nitrogen is not
available to living
things.
 The red stuff on the
tip of matches is
Oxygen Family or Chalcogens
 Elements in group 16
 Oxygen is necessary
for respiration.
 Many things that stink,
contain sulfur (rotten
eggs, garlic,
skunks,etc.)
Halogens
 Elements in group 17
 Very reactive, volatile,
diatomic, nonmetals
 Always found combined
with other element in
nature .
 Used as disinfectants
and to strengthen teeth.
GROUPS OF ELEMENTS IN
PERIODIC TABLE
NONMETALS
Second most amount of elements.
Elements found to the right of the heavy
black line on periodic table.
Properties that most nonmetals exhibit:
GROUPS OF ELEMENTS IN
PERIODIC TABLE
NONMETALS (cont.)
Chemical Properties:
Tends to form negative ions
In HCl – no reaction
In CuCl2 – no reaction
GROUPS OF ELEMENTS IN
PERIODIC TABLE
METALLOIDS
Elements that straddle the heavy black
line
Some discrepancy in number(6,7, or 8)
Combination of metallic and nonmetallic
properties.
GROUPS OF ELEMENTS IN
PERIODIC TABLE
NOBLE GASES
Elements found in group 18.
Extremely unreactive elements.
The Noble Gases
The Noble Gases
 Elements in group 18
 VERY unreactive,
monatomic gases
 Used in lighted “neon”
signs
 Used in blimps to fix
the Hindenberg
problem.
 Have a full valence
shell.
TRENDS IN PERIODIC TABLE
PHYSICAL PROPERTIES (cont.)
Boiling Point
Left to Right – increase through metals
then decreases through nonmetals
Top to Bottom – decreases in metals
and increase in nonmetals
TRENDS IN PERIODIC TABLE
REACTIVITY (cont.)
Nonmetals
Trend from left to right – increase
Trend from top to bottom – decrease
TRENDS IN PERIODIC TABLE
REACTIVITY
Metals
Trend from left to right – decrease
Trend from top to bottom – increase
Factors Affecting Chemical Trends
Nuclear Charge – strength of the nucleus
The larger the nuclear charge, the stronger the pull on the last electron
Sublevel Stability
An electron from a full or half-full sublevel requires additional
energy to be removed.
Shielding effect – electrons between nucleus and outer electron
The greater the shielding effect, the less the pull on the last electron.
Radius – distance from nucleus to outer electron
The greater the distance between the nucleus and the outer
electrons of an atom, the less the pull on the last electron.
Smoot, Price, Smith, Chemistry A Modern Course 1987, page 189
Periodic Trends in Atomic Radii
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 175
TRENDS IN PERIODIC TABLE
IONIC RADII
 Definition – distance from nucleus to outer edge
of ion
 Trend for more positive ion – decreases
Rationale – increasing relative nuclear charge
 Trend for more negative ion – increases
Rationale – decreasing relative nuclear charge
ANIONS BIGGER THAN CATIONS IN A GIVEN
PERIOD!!!!
Periodic Trends in Ionic Radii
IONIC RADII
1
2
Li1+
Be2+
0.60
Na1+
0.95
K1+
1.33
3
0.65
Ca2+
0.99
Al3+
0.50
Ga3+
0.62
In3+
Rb1+
1.48
Sr2+
1.13
6
N3-
O2-
1.71
0.31
Mg2+
5
0.81
1.40
S21.84
7
F11.36
Cl11.81
Br1-
Se21.98
1.85
I1-
Te22.21
2.16
Tl3+
Cs1+
1.69
Ba2+
1.35
0.95
= 1 Angstrom
Trends in Atomic and Ionic Size
Metals
Nonmetals
Group 1
Group 13
Group 17
e
e
Li+
Li
152
F
64
60
e
e
Na+
Na
95
e
e
136
e
Al3+
Al
143
F1-
50
Cl
Cl1-
99
186
181
e
e
K+
Br
K
227
133
Cations are smaller than parent atoms
114
Br-1195
Anions are larger than parent atoms
e
Li+
Li
152
60
e
e
Li+
e
Li
Li +
e
Lithium ion
Lithium atom
Lithium atom
60
Lithium ion
TRENDS IN PERIODIC TABLE
FIRST IONIZATION ENERGY
Definition – amount energy needed to
remove the outer most electron
Trend from left to right – increases
Rationale – increased nuclear charge
Trend from top to bottom – decreases
Rationale – increased energy levels and
shielding effect
TRENDS IN PERIODIC TABLE
ELECTRON AFFINITY
Definition – the attraction of an atom for an
electron
Trend from left to right – increases
Rationale – increasing nuclear charge
Trend from top to bottom – decreases
Rationale – increasing energy levels and
shielding effect
TRENDS IN PERIODIC TABLE
ELECTRONEGATIVITY
Definition – the tendency of an atom
to attract electrons to itself when it is
combined with another atom
Trend from left to right – increases
Trend from top to bottom – decreases
Nuclear charge increases
Shielding increases
Atomic radius increases
Ionic size increases
Ionization energy decreases
Electronegativity decreases
Summary of Periodic Trends
Shielding is constant
Atomic radius decreases
Ionization energy increases
Electronegativity increases
Nuclear charge increases
1A
0
2A
Ionic size (cations)
decreases
3A 4A 5A 6A 7A
Ionic size (anions)
increases
Electronegativities
1A
1
Period
2
3
4
5
6
7
8A
H
2.1
2A
3A
4A
5A
6A
7A
Li
Be
B
C
N
O
F
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Al
Si
P
S
Cl
1.5
1.8
2.1
2.5
3.0
Na Mg
1.2
3B
4B
5B
6B
K
Ca Sc
Ti
V
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br
0.8
1.0
1.3
1.5
1.6
1.6
1.7
1.6
1.8
Rb Sr
Y
Zr Nb Mo Tc Ru Rh Pd Ag Cd
In
Sn Sb Te
0.8
1.2
1.4
1.6
1.8
1.9
2.2
2.2
2.2
1.7
1.7
1.8
Cs Ba
La*
Hf
Ta
W
Re Os
Ir
Pt Au Hg
Tl
Pb Bi
Po At
0.7
1.1
1.3
1.5
1.7
1.9
2.2
2.2
1.8
1.8
2.0
1.0
0.9
y
Fr
Ra Ac
0.7
0.9
1.1
8B
7B
1.5
1.8
2.2
1.8
1B
2B
0.9
1.8
1.9
1.9
2.4
1.9
2.0
1.9
1.9
2.4
2.1
* Lanthanides: 1.1 - 1.3
yActinides:
1.3 - 1.5
Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 373
Below 1.0
2.0 - 2.4
1.0 - 1.4
2.5 - 2.9
1.5 - 1.9
3.0 - 4.0
2.8
I
2.5
2.2