Chemistry Reference
In-Depth Information
My first attempt in this direction was as follows: I selected the substances with the smallest
atomic weights and arranged them according to the magnitude of their atomic weights [i.e.
primary classification
]. It became apparent that there existed, so to speak, a periodicity in
the properties (even with regard to valency) of the simple substances [i.e
. periodic law
],
when one element followed another according to a linear arithmetical arrangement of their
atomic weights. [Secondary classification therefore led to]:
Li
¼
7
Be
¼
9.4
B
¼
11
C
¼
12
N
¼
14
O
¼
16
F
¼
19
Na
¼
23
Mg
¼
24
Al
¼
27.4
Si
¼
28
P
¼
31
S
¼
32
Cl
¼
35.5
K
¼
39
Ca
¼
40
Ti
¼
50
V
¼
51
-
-
-
In the division of elements with an atomic weight greater than 100 we encounter a
completely analogous series:
Ag
¼
108
Cd
¼
112
Ur
¼
116
Sn
¼
118
Sb
¼
122
Te
¼
128
J
¼
127
It is seen that Li, Na, K, Ag show the same relationship to one another as do N, P, V, Sb, etc.
[i.e. the formation of elementary groups as a result of
secondary classification
].
21
11.1.6 Primary Versus Secondary Groups
One can conclude at this point that natural, elementary groups (e.g. Li, Na, K,
...
,
Ag) are formed during the secondary classification. Within such a vertical group,
the atomic weights of the congeners vary in a stepwise manner.
22
In the case of the
alkali metals {Li, Na, K,
...
, Ag}, for example, one notices the following sequence
of
108. We will
denominate such a natural group of elements by the term
secondary group
, the
members of which will be called
secondary elements
. Hence, a secondary group is
defined and recognised as follows:
jumps
between the atomic weights: 7
23
39
➠
...
➠
'
'
➠
➠
1. Secondary groups are formed during the secondary classification of the elements;
2. There exists a stepwise relationship between the atomic weights of the congeners.
Some examples of secondary groups are the alkali metals, the alkaline earth metals,
the halogens, and the noble gases.
In sharp contrast with this type of natural groups, some other groups, such as the
cerium group {Ce, La, Di}, are formed at an earlier stage of the construction
methodology, namely during the
primary classification
. Worded somewhat differ-
ently, due to the fact that the elements constituting such groups succeed one another
sequentially in the Mendeleev Line (e.g. Ce
95), the formation
of these groups will be noticed during the primary classification. Within such a
horizontal group, the atomic weight of the congeners will remain almost constant.
¼
92, La
¼
94, Di
¼
21
Mendeleev (1869b/t), op. cit., p. 25. (see note 16)
22
Congeners are elements in the same group of the periodic system.
