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10th Mar 2020 @ 4 min read
Julius Lothar Meyer was a German chemist. In 1864, he published the first version of his periodic table through his book Die modernen Theorien der Chemie. The table consisted of 28 elements arranged from the left to right as shown below.
|Element||-||-||-||-||Li = 7.03||Be = 9.3|
|C = 12.0||N = 14.04||O = 16.00||F = 19.0||Na = 23.05||Mg = 24.0|
|Si = 28.5||P = 31.0||S = 32.07||Cl = 35.46||K = 39.13||Ca = 40.0|
|-||As = 75.0||Se = 78.8||Br = 79.97||Rb = 85.4||Sr = 87.6|
|Sn = 117.6||Sb = 120.6||Te = 128.3||I = 126.8||Cs = 133.0||Ba = 137.1|
|Pb = 207.0||Bi = 208.0||-||-||Tl = 204||-|
From the previous table, it is clear that he not only ordered the elements with increasing atomic weights but also grouped them according to their valencies. The valence of an element is the combining power of the element with other elements. For example, the elements of the first column—C, Si, Sn, Pb—combine with hydrogen to form tetrahydride—CH4, SiH4, SnH4, PbH4. Thus, their valency is 4. Similarly, N, O, F, Na, Mg and other elements combine to form NH3, H2O, HF, NaH, MgH2… The grouping of elements based on their valency is the grouping them based on their chemical properties.
Also, the empty slots in the table were an indication of the existence of undiscovered elements.
Meyer plotted the graph of the atomic volume (molar volume) vs atomic weight. He noticed a series of maxima and minima. The most electropositive elements (Li, Na, K…) were observed at the peaks while the electronegative elements occurred at the ascent of the peaks.
If we look at the above chart closely, all the elements between two consecutive maxima belong to the same period in the modern periodic table. For example, Li, Be, B, C, N, O, and F are placed in period 2. The trend in the chart depicts the periodicity of the elements.
He published the finalized version of his periodic table in 1870. In this table, he incorporated additional elements, particularly transition metals known at that time. The table was divided into nine groups. This table was the transpose of his 1964's table, i.e., the rows were turned into columns and the columns into the rows.
|Element||B = 11.0||Al = 27.3||-||In = 113.4||Tl = 202.7|
|C = 11.97||Si = 28||-||Sn = 117.8||Pb = 206.4|
|Ti = 48||Zr = 89.7||-|
|N = 14.01||P = 30.9||As = 74.9||Sb = 122.1||Bi = 207.5|
|V = 51.2||Nb = 93.7||Ta = 182.2|
|O = 15.96||S = 31.98||Se = 78||Te = 128||-|
|Cr = 52.4||Mo = 95.6||W = 183.5|
|-||F = 19.1||Cl = 35.38||Br = 79.75||I = 126.5||-|
|Mn = 54.8||Ru = 103.5||Os = 198.6|
|Fe = 55.9||Rh = 104.1||Ir = 196.7|
|Co = Ni |
|Pd = 106.2||Os = 196.7|
|Li = 7.01||Na = 22.99||K = 39.04||Rb = 85.2||Cs = 132.7||-|
|Ag = 107.66||Au = 196.2|
|Be = 9.8||Mg = 23.9||Ca = 39.9||Sr = 87.0||Ba = 136.8||-|
|Zn = 64.9||Cd = 111.6||Hg = 199.8|
The above table is taken from Meyer's paper published in Annalen der Chemie, Supplementband (1870).
Julius Lothar Meyer was born to Friedrich Meyer, who was a physician, and Anna Biermann in Varel, Germany. His early education was centered on pathology and medicine. He completed his Ph.D. in chemistry in 1958.
In 1862, he started working on his book Die modernen Theorien der Chemie, which described the first version of his periodic table. The table was superior to any of its predecessors since it categorized the elements by their valencies. Meyer drafted his final version of the table in 1968. Unfortunately, he did not publish it. It got published in 1970, one year after Mendeleev published his table.
Meyer predicted the existence of undiscovered elements but did not elaborate on the properties of unknown elements, which Mendeleev did. This is the primary reason why most people give the first credit to Mendeleev, not Meyer, for the development of the periodic table. In the year 1882, both were jointly honored the Davy Medal by the Royal Society of London for their contributions to the periodic table. It is surprising to note that both scientists were developing the same table and were completely unaware of each other's work for a considerable amount of time.
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