The Periodic
Table
Science has come a long way from thinking that air, water, earth, and
fire come together to form all objects and life on earth. Most of
naturally occuring elements were known back in the 1900's, but scientists
had no clear-cut picture of how to organize them. After all, there were
patterns that people recognized, but there needed to be a good way of
graphically representing these elements.
With all these elements that scientists have discovered, there
needed to be a good way to organize the elements. And, scientists
noticed that many of the elements had similar properties - therefore,
it made sense to group these elements together.
Mendeleev was a scientist who created the longest lasting version of the
periodic table. In fact, the modern day periodic table is essentially
just an expansion of his original table. He published a paper in 1869
which outlined his ideas for organizing the elements.
The following eight statements were contained in the paper:
- The elements, if arranged according
to their atomic weights show an evident periodicity of
properties.
- Elements which are similar as regards their chemical properties
have atomic weights which are either nearly the same value or which
increase regularly.
- The arrangement of the elements or of groups of elements in the
order of their atomic weights, corresponds with their so called
valencies.
- The elements which are most widely distributed in nature have small
atomic weights, and sharply defined properties. They are therefore typical
elements.
- The magnitude of the atomic weight determines the character of an
element.
- The discovery of many as yet unknown elements may be
expected.
- The atomic weight of an element may sometimes be corrected by the
aid of a knowledge of those of adjacent elements.
- Certain characteristic properties of the elements can be foretold
from their atomic weights.
Here is a picture of Mendeleev's table of the elements:
Here is a picture of the modern periodic table:
| Group |
1 |
2 |
|
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
| Period | |
| 1 |
1
H |
|
2
He |
|---|
| 2 |
3
Li |
4
Be |
|
5
B |
6
C |
7
N |
8
O |
9
F |
10
Ne |
|---|
| 3 |
11
Na |
12
Mg |
|
13
Al |
14
Si |
15
P |
16
S |
17
Cl |
18
Ar |
|---|
| 4 |
19
K |
20
Ca |
|
21
Sc |
22
Ti |
23
V |
24
Cr |
25
Mn |
26
Fe |
27
Co |
28
Ni |
29
Cu |
30
Zn |
31
Ga |
32
Ge |
33
As |
34
Se |
35
Br |
36
Kr |
|---|
| 5 |
37
Rb |
38
Sr |
|
39
Y |
40
Zr |
41
Nb |
42
Mo |
43
Tc |
44
Ru |
45
Rh |
46
Pd |
47
Ag |
48
Cd |
49
In |
50
Sn |
51
Sb |
52
Te |
53
I |
54
Xe |
|---|
| 6 |
55
Cs |
56
Ba |
* |
71
Lu |
72
Hf |
73
Ta |
74
W |
75
Re |
76
Os |
77
Ir |
78
Pt |
79
Au |
80
Hg |
81
Tl |
82
Pb |
83
Bi |
84
Po |
85
At |
86
Rn |
|---|
| 7 |
87
Fr |
88
Ra |
** |
103
Lr |
104
Rf |
105
Db |
106
Sg |
107
Bh |
108
Hs |
109
Mt |
110
Uun |
111
Uuu |
112
Uub |
113
Uut |
114
Uuq |
115
Uup |
116
Uuh |
117
Uus |
118
Uuo |
|---|
| | |
| *Lanthanoids |
* |
57
La |
58
Ce |
59
Pr |
60
Nd |
61
Pm |
62
Sm |
63
Eu |
64
Gd |
65
Tb |
66
Dy |
67
Ho |
68
Er |
69
Tm |
70
Yb |
|
|
|---|
| **Actinoids |
* |
89
Ac |
90
Th |
91
Pa |
92
U |
93
Np |
94
Pu |
95
Am |
96
Cm |
97
Bk |
98
Cf |
99
Es |
100
Fm |
101
Md |
102
No | | |
|---|
The rows of the periodic table are called "groups" or "families" and the
columns are
called "periods." So, all elements under oxygen fall in the oxygen group
or the oxygen family. All of the second row are included in period two.
There are some special names for a few groups:
Group 1 - Alkali Metals
Group 2 - Alkaline Earth Metals
Group 17 - Halogens
Group 18 - Noble Gases
The group of elements colored in red are considered the transition metals.
The group of elements colored in green are the rare earth metals. The
group of elements in yellow are called the non-metals, and the group of
elements in blue are called metals.
Here is the periodic table arranged in a different manner:
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