atom THE PERIODIC TABLE atom

Sections of this page :
  1. History
  2. Arrangement
  3. First row elements
  4. Other related sites

HISTORY

The first peroidic table appeared in 1869 and is credited to a Russian chemist, Dimitri Mendeleev, although another was created at about the same time by Julius Meyer, a German physicist. The Mendeleev table is the basis of the one used today, and is largely unchanged.

Dimitri Mendeleev

mendeleev picture

The Mendeleev table is the basis of the one used today, and is largely unchanged. It was designed as a chart which would allow properties of the elements to be predicted, but it also predicted elements which have only recently been discovered, and which fit exactly into the table. The only thing left to argue about are the names of the new elements!

Mendeleev arranged the elements according to his periodic law, which states

"The properties of the elements are a peroidic function of their atomic mass"

When he arranged the elements like this, he found certain elements grouped themselves into vertical families, what are now known as groups . The horizontal rows formed are known as periods. Perhaps the most important observation was the relationship between atomic weights and proprties of the elements, and the trend of elements in each group to have consistantly high or low values of certain properties.

Dimitri Mendeleev created this, the original, periodic table.

Reihen
Gruppe I.
-
R2O

Gruppe II.
-
RO 

Gruppe III.
-
R2O3

Gruppe IV.
RH4
RO2

Gruppe V.
RH3
R2O5

Gruppe VI.
RH2
RO3

Gruppe VII.
RH
R2O7

Gruppe VIII.
-
RO4

1 H = 1              
2 Li = 7
Be = 9,4
B = 11
C = 12
N = 14
O = 16
F = 19
 
3 Na = 23 Mg = 24 Al = 27,3 Si = 28 P = 31 S = 32 Cl = 35,5  
4 K = 39 Ca = 40 - = 44 Ti = 48 V = 51 Cr = 52 Mn = 55 Fe = 56, Co=59
Ni=59, Cu=63
5 (Cu = 63) Zn = 65 - = 68 - = 72 As = 75 Se = 78 Br = 80  
6 Rb = 85 Sr = 87 ?Yt = 88 Zr = 90 Nb = 94 Mo = 96 - = 100 Ru=104, Rh=104
Pd=106, Ag=108
7 Ag = 108 Cd = 112 In = 113 Sn = 118 Sb = 122 Te = 125 J = 127  
8 Cs = 133 Ba = 137 ?Di = 138 ?Ce = 140 - - - -  -  -  -
9 (-) - - - - - -  
10 - - ?Er = 178 ?La = 180 Ta = 182 W = 184 - Os=195, Ir=197,
Pt=198, Au=199
11 (Au = 199) Hg = 200 Tl = 204 Pb = 207 Bi = 208 - -  
12 - - - Th = 231 - U = 240 - -  -  -  -

There were inconsistancies in this first table, but these were rectified by Professor Mosley, a British physicist who modified the table by arranging the elements by atomic number, not atomic mass. Mosley's periodic law, based on atomic number is now regarded as correct.

This is a modern periodic table
Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
  1A 2A 3B 4B 5B 6B 7B 8B 1B 2B 3A 4A 5A 6A 7A 8A
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
 
lanthanides * 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
actinides ** 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

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ARRANGEMENT

Each of the vertical groups of the table are given a number, and this corresponds to the number of valence electrons each element in that group has. Each period is numbered according to how many occupied energy shells the elements in it have, so, although the elements considered on this page are known as the first row elements, they actually fall in period 2, hydrogen and helium being the only element in period 1.

Group 1 elements - Known as the alkali metals, these elements are unusually soft and highly reactive with water and oxygen.
Group 2 elements - Known as the alkali earth metals, but are not as soft or reactive as the Group 1 metals.
Group 3 to 12 elements - These are the transition metals, and do not have such uniform properties due to shielding effects on the inner electrons.
Group 13 to 18 elements - Known as the representative elements.
Group 17 - The halogens, which means "salt makers".
Group 18 - The noble gases. There are very few componds of these elements as they are so unreactive, with no desire to gain or lose electrons.

Although Mendeleev's table is by far the most practical and widely used, there has been some other tables made, for instance Stowe's physicists periodic table (1988), Benfey's periodic spiral (1960) and Zmaczynski's periodic triangle (1935).

To demonstrate the trends that do exist between elements, and to illustrate just how good the periodic table is at representing this, i have choosen the first row elements as they simply show the patterns which can be found throughout the periodic table.

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FIRST ROW ELEMENTS

This section is divided into information on the individual elements and periodic trends.

INDIVIDUAL ELEMENTS

The first row elements
Li Be B C N O F Ne

CLICK ON AN ELEMENT FOR FUTHER INFORMATION

PERIODIC TRENDS

This diagram illustrates clearly some of the main trends of the periodic table.

Periodic trends demonstrated by the first row elements
Covalent radius Electronegativity Effective nuclear charge Ionisation energy Atomic weight

CLICK ON A PROPERTY FOR MORE INFORMATION

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OTHER RELATED SITES

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Page written by Keira Stobie 01/05/97