The development of the Periodic Table (pre-16)

John Newlands

Could the original formulation of the Periodic Table be regarded as British? Just four years before Mendeleev announced his Periodic Table, John Alexander Reina Newlands wrote in Chemical News

 ‘If the elements are arranged in order of their equivalents [ie relative atomic masses in today’s terminology] with a few transpositions, it will be seen that elements belonging to the same group appear in the same horizontal line. Also the numbers of similar elements differ by seven or multiples of seven. Members stand to each other in the same relation as the extremities of one or more octaves of music. Thus in the nitrogen group phosphorus is the seventh element after nitrogen and arsenic is the fourteenth elements after phosphorus as is antimony after arsenic. This peculiar relationship I propose to call The Law of Octaves'.

Surely this was a prediction of patterns in the properties of the elements and described a Periodic Table?

Newlands thought that patterns were connected with the relative weights of atoms (we would now call them relative atomic masses – they were then called atomic weights) of different elements. Fortunately, in 1860 there had been a conference in Karlsruhe (Germany) which had made a more accurate list of these atomic weights than had previously been available. Not only had some values been slightly wrong through inaccurate measurements but some were half or a third of the correct value through false reasoning.  See Problems with relative atomic masses.

One difficulty was that only about 60 elements were known then (there are over 100 now), although fortunately most of the undiscovered ones were of higher relative atomic mass. Newlands listed those known in order of their atomic weight putting their position in this sequence alongside the symbol. He did not give a name to this position number. A copy of his table is shown below using the symbols Newlands used.

 

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 34

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

 

The pattern was perfect up to calcium then became less convincing as some metals appeared unlike the non-metals to their left. However a further seven elements later there was a greater similarity. Then Newlands was forced to sometimes put two elements in the same box so that after this similar elements would be in the same horizontal line. Di stood for didymium, which we now know is not an element at all but a mixture of two elements.

Note that Newlands did not always stick to a strict increase in number. He exchanged the positions of Zn and Y, presumably because he realised that Y resembled Bo (modern symbol B). The modern Periodic Table does not always show an increase in relative atomic masses for successive elements but it is a less common occurrence than in Newlands’ table.

On 1st March 1865, he described his ideas at a lecture at the Chemical Society (a forerunner of the Royal Society of Chemistry). The lack of spaces for undiscovered elements and the placing of two elements in one box were justifiably criticised but an unfair suggestion from Professor Foster was that he might have equally well listed the elements alphabetically. Foster was on the Publication Committee which refused to publish his paper, supposedly because it was of a purely theoretical nature. Humiliated, Newlands went back to his work as chief chemist at a sugar factory.

Four years later Mendeleev, unaware of Newlands' ideas, formulated an improved Periodic Table which gained acceptance, particularly because he left spaces for undiscovered elements, some of which were soon found with properties he predicted. As the Periodic Table became accepted, Newlands, understandably, claimed its first publication. However the Chemical Society did not back his claims. Indeed the final years of his working life were spent running a family chemical business with his brother.

The Chemical Society made some amends for discrediting him by asking him in 1884 to give a lecture on the Periodic Law. However its full recognition of his discovery waited until 1998, the centenary of his death, when the Royal Society of Chemistry oversaw the placing of a blue commemorative plaque on the wall of his birthplace. Note its inscription.

Reproduced courtesy of Gordon Woods

Questions

Q 1.     Newlands was the first person to give elements a 'position number'.

           (a) What do we call this today?

           (b) What property of the atomic nucleus is it related to?

Q 2.     (a) Which modern chemical group is missing from Newlands’ list of elements?

           (b) Apart from the omission of this whole group which element is the first omitted?

Q 3.     There are some unfamiliar symbols. Give the modern symbols and names of Gl and Bo.

Q 4.     Give the symbols of two elements which are at least two columns out of position because of extremely inaccurate atomic weights.

Q 5.     What do columns in the Newlands’ table almost correspond to in a modern Periodic Table?

Q 6.     Where do the alkali metals Li, Na, K etc appear in Newlands’ table? Give the names of the extra elements mixed with them. Why do you think Newlands thought they had a similarity with the alkali metals? (Hint; what important property do elements in the same group share?)

Q 7.     A musical octave goes from a note in one octave to the corresponding note in the next octave, eg from C to C, counting the notes at both ends. How many elements are there between Li and Na, or Na and K? What should this figure be? Explain the difference.

Q 8.     Give two ways in which the Newlands’ table is inferior to that of Mendeleev.

Click here to see the answers