Periodic Table |
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| What is the Periodic Table Showing? | Periodicity |
The INTERNET Database of Periodic Tables
There are thousands of periodic tables in web space, but this is the only comprehensive database of periodic tables & periodic system formulations. If you know of an interesting periodic table that is missing, please contact the database curator: Mark R. Leach Ph.D.
Use the drop menus below to search & select from the more than 1300 Period Tables in the database:
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Formulations 2020 to present day Formulations 2010 – 2019 Formulations 2000 – 2009 Formulations 1950 – 1999 Formulations 1900 – 1949 Formulations 1850 – 1899 Formulations 1800 – 1849 Formulations Before 1800 =================== All Periodic Tables by Date All Periodic Tables by Reverse Date All Periodic Tables, as Added to the Database All Periodic Tables, reverse as Added =================== 2026 2025 2024 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986 1985 1984 1983 1982 1981 1980 1979 1978 1977 1976 1975 1974 1973 1972 1971 1970 1969 1968 1967 1966 1965 1964 1963 1962 1961 1960 1959 1958 1957 1956 1955 1954 1953 1952 1951 1950 1949 1948 1947 1946 1945 1944 1943 1942 1941 1940 1939 1938 1937 1936 1935 1934 1933 1932 1931 1930 1929 1928 1927 1926 1925 1924 1923 1922 1921 1920 1919 1918 1917 1916 1915 1914 1913 1912 1911 1910 1909 1908 1907 1906 1905 1904 1903 1902 1901 1900 1899 1898 1897 1896 1895 1894 1893 1892 1891 1890 1889 1888 1887 1886 1885 1884 1883 1882 1881 1880 1879 1878 1877 1876 1875 1874 1873 1872 1871 1870 1869 1868 1867 1866 1865 1864 1863 1862 1861 1860 1859 1858 1857 1856 1855 1854 1853 1852 1851 1850 1844 1843 1842 1838 1836 1831 1830 1829 1825 1824 1817 1814 1813 1811 1808 1807 1804 1803 1802 1801 1800 1798 1794 1791 1789 1787 1783 1782 1781 1778 1775 1774 1772 1771 1766 1753 1751 1748 1735 1718 1700 1690 1687 1682 1671 1669 1624 1617 1520 1000 -300 -450 -800 -1000 -2000 -3500 -3750 -5000 -6000 -7000 -9000
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The 10 Periodic Tables most recently added to the database:
| Year: 2026 | PT id = 1365, Type = formulation |
Pairs and Squares Periodic Table
"Pairs and Squares" Periodic Table by Leonid A. Levin of Boston University
Leonid writes:
"All the tables [in the PT Database] share a common problem: their irregularity exceeds by far their periodicity.
"In my youth I was greatly bothered by this. Yet, taking advantage of a few patterns in atomic orbitals allows a complete elimination of all irregularities, putting all periods in a perfect pattern.This perfectly regular rendition would be much more comfortable, especially at one's first high school exposure to this Science symbol.I am attaching such "Pairs and Squares" rendition with a brief explanation."
"Read more in the full 'Pairs and Squares' paper, here."

| Year: 2007 | PT id = 1364, Type = formulation |
Distribuzione Peridica Degli Elemnti
Distribuzione Peridica Degli Elemnti – Periodic Distribution of Elements – by Leonello Paoloni.
From La Chimica nella Scuola, Sept. 2007, pp 111.
"Fig. 2. The periodic distribution of elements correlates with the group distribution of atomic electrons. Groups are formed so that all elements of the same family are found in corresponding positions (for example, the halogens are always in the second-to-last position in a group of six elements)." (Google Translate)

Thanks to Eric Scerri for the tip!
| Year: 1873 | PT id = 1363, Type = formulation review element |
Annual Report on the Progress of Chemistry and Related Areas of Other Sciences 1873
Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften. (Annual Report on the progress of chemistry and related areas of other sciences.) HathiTrust Index scanned reports 1847-1910.
The 1873 table of data is here.
Mark Leach writes:
"Every year the annual report started with a list of the known chemical elements and their atomic weights, however, to the modern eye there were many systematic errors. For example, oxygen (Sauerstoff) is given as having a weight of 8 which would have caused – due to the importance of oxides – other atomic weights to be out by a factor of 2 or 3. Once a list of correct atomic weights was known, it would be possible to construct a periodic table of the elements.
"In 1858 the Cannazzario letter gave more correct list of atomic weights and corrected the numerous stoichiometric errors that plagued chemistry at the time. Over the years from 1858 to 1873 the entries in the annual report gradually adopted the Cannazzario logic."

Notes:
- Didym D = 48 was actually a mixture of rare earth elements.
- Ilmenium, Il, was later found to be a mixture of niobium and tantalum.
- Generally, the elements missing had yet to be discovered (dates given below).
- The table below shows the progress from 1858 to 1873.
- By 1873 the only elements with incorrect atomic weights were the (at the time) somewhat obscure strontium, lanthanium, cerium and urananium.
- Previously, many elements were shown with two entries. Clearly, the stoichiometric and mass problems had largely been resolved (and the data agreed upon) by 1873.

Thanks to René and Mario Rodriguez for the tip!
| Year: 1872 | PT id = 1362, Type = formulation review element |
Annual Report on the Progress of Chemistry and Related Areas of Other Sciences 1872
Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften. (Annual Report on the progress of chemistry and related areas of other sciences.) HathiTrust Index scanned reports 1847-1910.
The 1872 table of data is here.
Mark Leach writes:
"Every year the annual report started with a list of the known chemical elements and their atomic weights, however, to the modern eye there were many systermatic errors. For example, oxygen (Sauerstoff) is given as having a weight of 8 which would have caused – due to the importance of oxides – other atomic weights to be out by a factor of 2 or 3. Once a list of correct atomic weights was known, it would be possible to construct a periodic table of the elements.
"In 1858 the Cannazzario letter gave more correct list of atomic weights and corrected the numerous stoichiometric errors that plagued chemistry at the time. Over the years from 1858 to 1873 the entries in the annual report gradually adopted the Cannazzario logic."
- Didym Di = 48 and 95 was actually a mixture of rare earth elements.
- The missing elements had yet to be discovered.
- Al = 13.7 and 27.4
- Ba = 68.5 and 137
- Be = 4.7 and 7.0
- Pb = 103.5 and 207
- Cd = 56 and 112
- Ca = 20 and 40
- Ce = 56 and 92
- Cr = 26 and 52
- Fe = 28 and 56
- Er = 56.3 and 112.6
- Ir = 99 and 198
- Co = 29.5 and 59
- C = 6 and 12
- Cu = 31.7 and 63.4
- La = 46.8 and 93.6
- Mg = 12 and 24
- Mn = 27.5 and 55
- Mo = 48 and 96
- Ni = 29.5 and 58
- Os = 100 and 200
- Pd = 53 and 106
- Pt = 99 and 198
- Hg = 100 and 200
- Rh = 52 and 104
- Ru = 52 and 104
- Si = 14 and 28
- O = 8 and 16
- S = 16 and 32
- Se = 39.5 and 79
- Sr = 43.8 and 87.6
- Te = 64 and 128
- Th = 57.8 and 115.6
- Ti = 25 and 50
- Wo = 92 and 184 (note change from W to Wo)
- Y = 29.8 and 59.7
- Zn = 32.5 and 65
- Sn = 59 and 118
- Zr = 45 and 90

Thanks to René and Mario Rodriguez for the tip!
| Year: 1871 | PT id = 1361, Type = formulation review element |
Annual Report on the Progress of Chemistry and Related Areas of Other Sciences 1871
Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften. (Annual Report on the progress of chemistry and related areas of other sciences.) HathiTrust Index scanned reports 1847-1910.
The 1871 table of data is here.
Mark Leach writes:
"Every year the annual report started with a list of the known chemical elements and their atomic weights, however, to the modern eye there were many systermatic errors. For example, oxygen (Sauerstoff) is given as having a weight of 8 which would have caused – due to the importance of oxides – other atomic weights to be out by a factor of 2 or 3. Once a list of correct atomic weights was known, it would be possible to construct a periodic table of the elements.
"In 1858 the Cannazzario letter gave more correct list of atomic weights and corrected the numerous stoichiometric errors that plagued chemistry at the time. Over the years from 1858 to 1873 the entries in the annual report gradually adopted the Cannazzario logic."
- Didym Di = 48 and 95 was actually a mixture of rare earth elements.
- The missing elements had yet to be discovered.
- Al = 13.7 and 27.4
- Ba = 68.5 and 137
- Be = 4.7 and 7.0
- Pb = 103.5 and 207
- Cd = 56 and 112
- Ca = 20 and 40
- Ce = 56 and 92
- Cr = 26 and 52
- Fe = 28 and 56
- Er = 56.3 and 112.6
- Ir = 99 and 198
- Co = 29.4 and 58.8
- C = 6 and 12
- Cu = 31.7 and 63.4
- La = 46.8 and 93.6
- Mg = 12 and 24
- Mn = 27.5 and 55
- Mo = 48 and 96
- Ni = 29.5 and 58
- Os = 100 and 200
- Pd = 53 and 106
- Pt = 99 and 198
- Hg = 100 and 200
- Rh = 52 and 104
- Ru = 52 and 104
- Si = 14 and 28
- O = 8 and 16
- S = 16 and 32
- Se = 39.5 and 79
- Sr = 43.8 and 87.6
- Te = 64 and 128
- Th = 57.86 and 115.72
- Ti = 25 and 50
- Wo = 92 and 184 (note change from W to Wo)
- Y = 30.8 and 61.6
- Zn = 32.5 and 65
- Sn = 59 and 118
- Zr = 45 and 90

Thanks to René and Mario Rodriguez for the tip!
| Year: 1870 | PT id = 1360, Type = formulation review element |
Annual Report on the Progress of Chemistry and Related Areas of Other Sciences 1870
Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften. (Annual Report on the progress of chemistry and related areas of other sciences.) HathiTrust Index scanned reports 1847-1910.
The 1870 table of data is here.
Mark Leach writes:
"Every year the annual report started with a list of the known chemical elements and their atomic weights, however, to the modern eye there were many systermatic errors. For example, oxygen (Sauerstoff) is given as having a weight of 8 which would have caused – due to the importance of oxides – other atomic weights to be out by a factor of 2 or 3. Once a list of correct atomic weights was known, it would be possible to construct a periodic table of the elements.
"In 1858 the Cannazzario letter gave more correct list of atomic weights and corrected the numerous stoichiometric errors that plagued chemistry at the time. Over the years from 1858 to 1873 the entries in the annual report gradually adopted the Cannazzario logic."
- Didym Di = 48 and 95 was actually a mixture of rare earth elements.
- The missing elements had yet to be discovered.
- Al = 13.7 and 27.4
- Ba = 68.5 and 137
- Be = 4.7 and 7.0
- Pb = 103.5 and 207
- Cd = 56 and 112
- Ca = 20 and 40
- Ce = 56 and 92
- Cr = 26.1 and 52.2
- Fe = 28 and 56
- Er = 56.3 and 112.6
- Ir = 99 and 198
- Co = 29.4 and 58.8
- C = 6 and 12
- Cu = 31.7 and 63.4
- La = 46.8 and 93.6
- Mg = 12 and 24
- Mn = 27.5 and 55
- Mo = 48 and 96
- Ni = 29.4 and 58.8
- Os = 100 and 200
- Pd = 53 and 106
- Pt = 99 and 198
- Hg = 100 and 200
- Rh = 52 and 104
- Ru = 52 and 104
- Si = 14 and 28
- O = 8 and 16
- S = 16 and 32
- Se = 39.5 and 79
- Sr = 43.8 and 87.6
- Te = 64 and 128
- Th =57.86 and 115.72
- Ti = 25 and 50
- Wo = 92 and 184 (note change from W to Wo)
- Y = 30.8 and 61.6
- Zn = 32.5 and 65
- Sn = 59 and 118
- Zr = 45 and 90

Thanks to René and Mario Rodriguez for the tip!
| Year: 1869 | PT id = 1359, Type = formulation review element |
Annual Report on the Progress of Chemistry and Related Areas of Other Sciences 1869
Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften. (Annual Report on the progress of chemistry and related areas of other sciences.) HathiTrust Index scanned reports 1847-1910.
The 1869 table of data is here.
Mark Leach writes:
"Every year the annual report started with a list of the known chemical elements and their atomic weights, however, to the modern eye there were many systermatic errors. For example, oxygen (Sauerstoff) is given as having a weight of 8 which would have caused – due to the importance of oxides – other atomic weights to be out by a factor of 2 or 3. Once a list of correct atomic weights was known, it would be possible to construct a periodic table of the elements.
"In 1858 the Cannazzario letter gave more correct list of atomic weights and corrected the numerous stoichiometric errors that plagued chemistry at the time. Over the years from 1858 to 1873 the entries in the annual report gradually adopted the Cannazzario logic."
- Didym Di = 48 and 95 was actually a mixture of rare earth elements.
- The missing elements had yet to be discovered.
- Al = 13.7 and 27.4
- Ba = 68.5 and 137
- Be = 4.7 and 7.0
- Pb = 103.5 and 207
- Cd = 56 and 112
- Ca = 20 and 40
- Ce = 56 and 92
- Cr = 26.1 and 52.2
- Fe = 28 and 56
- Er = 56.3 and 112.6
- Ir = 99 and 198
- Co = 29.4 and 58.8
- C = 6 and 12
- Cu = 31.7 and 63.4
- La = 46.8 and 93.6
- Mg = 12 and 24
- Mn = 27.5 and 55
- Mo = 48 and 96
- Ni = 29.4 and 58.8
- Os = 100 and 200
- Pd = 53 and 106
- Pt = 99 and 198
- Hg = 100 and 200
- Rh = 52 and 104
- Si = 14 and 28
- O = 8 and 16
- S = 16 and 32
- Se = 39.5 and 79
- Sr = 43.8 and 87.6
- Te = 64 and 128
- Th =57.86 and 115.72
- Ti = 25 and 50
- Wo = 92 and 184 (note change from W to Wo)
- Y = 30.8 and 61.6
- Zn = 32.5 and 65
- Sn = 59 and 118
- Zr = 44.8 and 89.6

Thanks to René and Mario Rodriguez for the tip!
| Year: 1868 | PT id = 1358, Type = formulation review element |
Annual Report on the Progress of Chemistry and Related Areas of Other Sciences 1868
Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften. (Annual Report on the progress of chemistry and related areas of other sciences.) HathiTrust Index scanned reports 1847-1910.
The 1868 table of data is here.
Mark Leach writes:
"Every year the annual report started with a list of the known chemical elements and their atomic weights, however, to the modern eye there were many systermatic errors. For example, oxygen (Sauerstoff) is given as having a weight of 8 which would have caused – due to the importance of oxides – other atomic weights to be out by a factor of 2 or 3. Once a list of correct atomic weights was known, it would be possible to construct a periodic table of the elements.
"In 1858 the Cannazzario letter gave more correct list of atomic weights and corrected the numerous stoichiometric errors that plagued chemistry at the time. Over the years from 1858 to 1873 the entries in the annual report gradually adopted the Cannazzario logic."
- Didym Di = 48 and 95 was actually a mixture of rare earth elements.
- The missing elements had yet to be discovered.
- Al = 13.7 and 27.4
- Ba = 68.5 and 137
- Be = 4.7 and 7.0
- Pb = 103.5 and 207
- Cd = 56 and 112
- Ca = 20 and 40
- Ce = 56 and 92
- Cr = 26.1 and 52.2
- Fe = 28 and 56
- Er = 56.3 and 112.6
- Ir = 99 and 198
- Co = 29.4 and 58.8
- C = 6 and 12
- Cu = 31.7 and 63.4
- La = 46.8 and 93.6
- Mg = 12 and 24
- Mn = 27.5 and 55
- Mo = 48 and 96
- Ni = 29.4 and 58.8
- Os = 100 and 200
- Pd = 53.3 and 106.6
- Pt = 99 and 198
- Hg = 100 and 200
- Rh = 52 and 104
- Si = 14 and 28
- O = 8 and 16
- S = 16 and 32
- Se = 39.7 and 79.4
- Sr = 43.8 and 87.6
- Te = 64 and 128
- Th =57.86 and 115.72
- Ti = 25 and 50
- Wo = 92 and 184 (note change from W to Wo)
- Y = 30.8 and 61.6
- Zn = 32.6 and 65.2
- Sn = 59 and 118
- Zr = 44.8 and 89.6

Thanks to René and Mario Rodriguez for the tip!
| Year: 1867 | PT id = 1357, Type = formulation review element |
Annual Report on the Progress of Chemistry and Related Areas of Other Sciences 1867
Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften. (Annual Report on the progress of chemistry and related areas of other sciences.) HathiTrust Index scanned reports 1847-1910.
The 1867 table of data is here.
Mark Leach writes:
"Every year the annual report started with a list of the known chemical elements and their atomic weights, however, to the modern eye there were many systermatic errors. For example, oxygen (Sauerstoff) is given as having a weight of 8 which would have caused – due to the importance of oxides – other atomic weights to be out by a factor of 2 or 3. Once a list of correct atomic weights was known, it would be possible to construct a periodic table of the elements.
"In 1858 the Cannazzario letter gave more correct list of atomic weights and corrected the numerous stoichiometric errors that plagued chemistry at the time. Over the years from 1858 to 1873 the entries in the annual report gradually adopted the Cannazzario logic."
- Didym Di = 48 and 95 was actually a mixture of rare earth elements.
- The missing elements had yet to be discovered.
- Al = 13.7 and 27.4
- Ba = 68.5 and 137
- Be = 4.7 and 7.0
- Pb = 103.5 and 207
- Cd = 56 and 112
- Ca = 20 and 40
- Ce = 56 and 92
- Cr = 26.1 and 52.2
- Fe = 28 and 56
- Ir = 99 and 198
- Co = 29.4 and 58.8
- C = 6 and 12
- Cu = 31.7 and 63.4
- La = 46.8 and 93.6
- Mg = 12 and 24
- Mn = 27.5 and 55
- Mo = 48 and 96
- Nb = 47 and 94
- Ni = 29.4 and 58.8
- Os = 99.6 and 199.2
- Pd = 53.3 and 106.6
- Pt = 98.7 and 197.4
- Hg = 100 and 200
- Rh = 52.2 and 104.4
- Si = 14 and 21 and 28
- O = 8 and 16
- S = 16 and 32
- Se = 39.7 and 79.4
- Sr = 43.8 and 87.6
- Ta = 68.8 and 172
- Te = 64 and 128
- Ti = 25 and 50
- Th =57.86 and 115.72
- W = 92 and 184
- Y = 30.8 and 61.6
- Zn = 32.6 and 65.2
- Sn = 59 and 118
- Zr = 22.4 and 33.6 and 44.8 and 89.6

Thanks to René and Mario Rodriguez for the tip!
| Year: 1866 | PT id = 1356, Type = formulation review element |
Annual Report on the Progress of Chemistry and Related Areas of Other Sciences 1866
Jahresbericht über die Fortschritte der Chemie und verwandter Theile anderer Wissenschaften. (Annual Report on the progress of chemistry and related areas of other sciences.) HathiTrust Index scanned reports 1847-1910.
The 1866 table of data is here.
Mark Leach writes:
"Every year the annual report started with a list of the known chemical elements and their atomic weights, however, to the modern eye there were many systermatic errors. For example, oxygen (Sauerstoff) is given as having a weight of 8 which would have caused – due to the importance of oxides – other atomic weights to be out by a factor of 2 or 3. Once a list of correct atomic weights was known, it would be possible to construct a periodic table of the elements.
"In 1858 the Cannazzario letter gave more correct list of atomic weights and corrected the numerous stoichiometric errors that plagued chemistry at the time. Over the years from 1858 to 1873 the entries in the annual report gradually adopted the Cannazzario logic."
- Didym Di = 48 and 95 was actually a mixture of rare earth elements.
- The missing elements had yet to be discovered.
- Al = 13.7 and 27.4
- Ba = 68.5 and 137
- Be = 4.7 and 7.0
- Pb = 103.5 and 207
- Cd = 56 and 112
- Ca = 20 and 40
- Ce = 56 and 92
- Cr = 26.1 and 52.2
- Fe = 28 and 56
- Ir = 99 and 198
- Co = 29.4 and 58.8
- C = 6 and 12
- Cu = 31.7 and 63.4
- La = 46.8 and 93.6
- Mg = 12 and 24
- Mn = 27.5 and 55
- Mo = 48 and 96
- Nb = 47 and 94
- Ni = 29.4 and 58.8
- Os = 99.6 and 199.2
- Pd = 53.3 and 106.6
- Pt = 98.7 and 197.4
- Hg = 100 and 200
- Rh = 52.2 and 104.4
- Si = 14 and 21 and 28
- O = 8 and 16
- S = 16 and 32
- Se = 39.7 and 79.4
- Sr = 43.8 and 87.6
- Ta = 68.8 and 172
- Te = 64 and 128
- Ti = 25 and 50
- Th = 57.86 and 115.72
- W = 92 and 184
- Zn = 32.6 and 65.2
- Sn = 59 and 118
- Zr = 22.4 and 33.6 and 44.8 and 89.6

Thanks to René and Mario Rodriguez for the tip!
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| What is the Periodic Table Showing? | Periodicity |
© Mark R. Leach Ph.D. 1999 –
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