Unit 1 Module 3 The Periodic Table - Pearson Schools

Alexandre-Emile Béguyer de Chancourtois
The French geologist Alexandre-Emile Béguyer de Chancourtois devised an early form of the
Periodic Table. In 1862 he arranged elements in a spiral on a cylinder, ordered by increasing
atomic weight. Elements with similar properties were aligned vertically.
John Newlands
The English chemist John Newlands was the first person to devise a Periodic Table of the
elements arranged in order of their relative atomic weights (now called relative atomic masses).
Building on Döbereiner’s work with ‘triads’, in 1865 he put forward his ‘law of octaves’, which
states that:
Module 3
The Periodic Table
The Periodic Table: searching for order
Any given element will exhibit analogous behaviour to the
eighth element following it in the table.
H 1 F 8 Cl 15 Co & Ni 22 Br 29 Pd 36 I 42 Pt & Ir 50
Li 2 Na 9 K 16 Cu 23 Rb 30 Ag 37 Cs 44 Tl 53
Gl 3 Mg 10 Ca 17 Zn 25 Sr 31 Cd 38 Ba & V 45 Pb 54
Bo 4 Al 11 Cr 18 Y 24 Ce & La 33 U 40 Ta 46 Th 56
C 5 Si 12 Ti 19 In 26 Zr 32 Sn 39 W 47 Hg 52
N 6 P 13 Mn 20 As 27 Di & Mo 34 Sb 41 Nb 48 Bi 55
O 7 S 14 Fe 21 Se 28 Ro & Ru 35 Te 43 Au 49 Os 51
Figure 3 John Newlands
Table 1 Newlands’ arrangement of elements in octaves
• Newlands’ arrangement showed all known elements arranged in seven ‘octaves’.
• The elements are ordered by the atomic weights that were known at the time. They were
numbered sequentially to show the order of atomic weights.
• In Newlands’ table, periods and groups are shown going down and across the table,
respectively – the opposite from our modern Periodic Table.
Newlands also altered the order of some elements, so that those with similar properties
appeared in the same row. In Table 1 above, some similarities have been picked out in colour.
Unfortunately, he left no gaps for elements that had yet to be discovered. Consequently, the
addition of a single new or missing element would throw the entire table out. The table did
highlight similarities between certain compounds, but contained many groupings for which
there were none. His Di (‘didymium’) was later found to be a mixture of two elements,
praseodymium and neodymium.
Note that none of the noble gases, which had yet to be discovered, appear in Newlands’ table.
Notice also that some symbols have since been changed (Bo is now B, for example).
Perhaps Newlands’ biggest mistake was the use of the musical term ‘octave’, which prompted
ridicule from some other scientists. One scientist suggested that similarities might just as easily
be found if the elements were arranged alphabetically.
Dmitri Mendeleev
Four years after Newlands published his law of octaves, the Russian chemist Dmitri Mendeleev
independently published a more advanced form of the Periodic Table, also based on atomic
masses. This forms the basis of the version we use today, which is arranged by atomic number.
While Newlands’ law of octaves represented the first application of periods to the table,
Mendeleev’s version is widely regarded as one of the most important developments in
chemistry.
Questions
1 Döbereiner proposed the ‘Law
of Triads’.
Use modern relative atomic
mass values to see how well this
law works for:
(a) Ca, r Sr and Ba Ba;
(b) Cl, Br and I;
(c) Li, Na and K.
2 Look at Newlands’ Periodic
Table set out in Table 1.
(a) Identify the elements that
Newlands placed out of
order, according to their
atomic weights.
(b) What term is given to the
sequence of these elements
in the modern Periodic
Table?
(c) What are the modern
symbols and names for the
elements Gl and Bo?
(d) Which names in the modern
Periodic Table correspond to
the rows and columns in
Newlands’ Periodic Table?
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