The combination of experimental data and theoretical insight supports a more nuanced understanding of complex periodic trends and non-periodic phenomena. While it is essential that Periodic Tables display important trends in element chemistry we need to keep our eyes open for unexpected chemical behavior in ambient, near ambient, or unusual conditions. Simplified, artistic, or economic tables are relevant to educational and cultural fields, while practicing chemists profit more from “chemical tables of chemical elements.” Such tables should incorporate four aspects: (i) typical valence electron configurations of bonded atoms in chemical compounds (instead of the common but chemically atypical ground states of free atoms in physical vacuum) (ii) at least three basic chemical properties ( valence number, size, and energy of the valence shells), their joint variation across the elements showing principal and secondary periodicity (iii) elements in which the (sp) 8, (d) 10, and (f) 14 valence shells become closed and inert under ambient chemical conditions, thereby determining the “fix-points” of chemical periodicity (iv) peculiar elements at the top and at the bottom of the Periodic Table. Such tables have been designed with the aim of either classifying real chemical substances or emphasizing formal and aesthetic concepts. To this end, a graphical display of the chemical properties of the elements, in the form of a Periodic Table, is the helpful tool. Comprehensive overviews of the chemistry of the elements and their compounds are needed in chemical science.
![color coded periodic table 2018 color coded periodic table 2018](https://d2gg9evh47fn9z.cloudfront.net/800px_COLOURBOX13301623.jpg)
The chemical elements are the “conserved principles” or “kernels” of chemistry that are retained when substances are altered. 4Department of Chemistry, Southern University of Science and Technology, Shenzhen, China.3Department of Chemistry, University of Siegen, Siegen, Germany.2Charles Sturt University, Wagga Wagga, NSW, Australia.1Department of Chemistry, Tsinghua University, Beijing, China.