A table or chart of nuclides is a two-dimensional graph of isotopes of the elements, in which one axis represents the number of neutrons and the other represents the number of protons in the atomic nucleus. Each point plotted on the graph thus represents a nuclide of a known or hypothetical chemical element. This system of ordering nuclides can offer a greater insight into the characteristics of isotopes than the better-known periodic table, which shows only elements and not their isotopes. The chart of the nuclides is also known as the Segrè chart, after the Italian physicist Emilio Segrè.
Fragment of table of nuclides as seen on a monument in front of University of Warsaw's Centre of New Technologies, with the four elements named by or for Polish scientists shown in the title ("including Po, Ra, Cm, Cn") and below the table: polonium (84Po) discovered in 1898 radium (88Ra) discovered in 1898 curium (96Cm) discovered in 1944 copernicium (112Cn) discovered in 1996
Isotopes are distinct nuclear species of the same chemical element. They have the same atomic number and position in the periodic table, but differ in nucleon numbers due to different numbers of neutrons in their nuclei. While all isotopes of a given element have similar chemical properties, they have different atomic masses and physical properties.
In the bottom right corner of J. J. Thomson's photographic plate are the separate impact marks for the two isotopes of neon: neon-20 and neon-22.
