Question

Commentb on the pasition of helium in periodic table

Answer 1

in the periodic table helium is situated on the first period and 18th group

Answer 2

Helium and neon, the two lightest noble gases, have been traditionally positioned by IUPAC in the Group 18 of the Periodic Table of Elements, together with argon, and other unreactive or moderately reactive gaseous elements (krypton, xenon, radon), and oganesson. In this account we revive the old discussion on the possible placement of helium in the Group 2, while preserving the position of neon in Group 18. We provide quantum-chemical arguments for such scenario—as well as other qualitative and quantitative arguments—and we describe previous suggestions in the literature which support it or put it into question. To this author’s own taste, He should be placed in Group 2.

Keywords

Periodic Table Hydrogen Fluorine Beryllium Noble gases Helium Neon Argon Reactivity Electronic structure Ionization potential Electron affinity 

This work commemorates the 150th anniversary of the discovery of helium and the 120th of neon.

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The traditional depiction of the periodic system, which has been taught to this author in primary school in the 1980s, has been the so-called short version (SPT), with the division to A (main group) and B (transition metal) Group elements (Fig. 1top). This version follows to some extent the early formulation by Mendeleyev, and introduces Group VIII containing Fe, Co, Ni, and their heavier analogues. Here, noble gases stand out as Group 0, to emphasize lack of room for them in the original Mendeleyev’s formulation; this happily coincides with their null (or weak at best) bond-forming ability. On the other hand, the Periodic Table recommended to this author during education in the comprehensive school a decade later was the so-called long version (LPT), with the transition metal elements clearly separated from the main group ones (Fig. 1 bottom, Roman numerals). Here, the A and B Groups still persisted. Finally, the freshman years of the 1990s brought another, more subtle, modification: the giant Periodic Table depicted in the Grand Aula of the Chemistry Faculty of the University of Warsaw corresponds to a long version, with noble gases placed in the last Group of the chart, the Group numbering now running from 1 to 18 in Arabic rather than Roman numbers (Fig. 1 bottom, Arabic numerals). Now, the old Group VIII encompasses three modern Groups: 8, 9 and 10. This version of the Table survived in the main didactic room to this day, except for a few elements being given their new IUPAC-recommended names (Francl 2009). It may seem that with the naming of the last superheavy elements in 2016, the history of the formulation of the Periodic Chart is closed, or at least it will rest until the new Period is opened due to a synthesis of a Z > 118 element (Seaborg 1969; Pyykkö 2011).