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article imageEssential Science: What are the limits of the periodic table?

By Tim Sandle     Jul 9, 2018 in Science
This year marks the 150th anniversary of the first periodic table of elements. At stages the table has been added to, as new elements are discovered or, these days, ‘manufactured’. Just how far can the table keep growing?
This is a question posed by Michigan State University professor in a new opinion-based science paper. The researcher in question is Witek Nazarewicz, who holds the distinction of being the Hannah Distinguished Professor of Physics.
Nazarewicz reflects by considering the most recent additions to the table. The most recent four elements incorporated were: nihonium, moscovium, tennessine, and oganesson, granted by the International Union of Pure and Applied Chemistry (IUPAC). These elements, which have the atomic numbers 113, 115, 117, and 118, respectively, were added after four years of discussions among scientists.
Elements are added to the periodic table based on the number of protons in the nucleus. These shape the chemical properties and allocate a place within the periodic table.
Periodic Table
The periodic table is an arrangement, in table form, of the chemical elements. The elements are ordered by atomic number, electron configuration, and recurring chemical properties. The arrangement thus shows periodic trends. The general pattern is that within one row (or ‘period’) the elements are metals to the left and non-metals to the right. The arrangement also means that elements which have similar chemical behaviors are placed in the same column.
The first periodic tables were published by Russian chemistry professor Dmitri Mendeleev and German chemist Julius Lothar Meyer, independently in 1869 and 1870, respectively. Both researchers produced their tables by listing the elements in rows or columns in order of atomic weight.
New elements
Newly discovered elements are elements that possess more than 104 protons. These are described as "superheavy" elements and they form part of a vast and unknown arena that chemists are attempting to uncover. There are theories that predict that atoms with up to 172 protons can physically form a nucleus (where these are bound together by nuclear forces). Why these elements are hard to detect is because although a force stops their disintegration, this only lasts fractions of a second.
Terbium is a chemical element with symbol Tb and atomic number 65. It is a silvery-white  rare earth...
Terbium is a chemical element with symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, ductile, and soft enough to be cut with a knife. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas.
Unknown, via Wikipedia
Moreover, these elements can only be shown to exist under laboratory conditions. This presents considerably challenges for how researchers attempt to define and understand "atoms." The school book style descriptor of a central nucleus with electrons orbiting it akin to planets orbiting a star.
According to Laboratory Manager magazine, the search for element 119 carries on across several research institutes, including the Joint Institute for Nuclear Research in Russia, at GSI in Germany, and RIKEN in Japan.
What’s interesting here is if element 119 is discovered, this will add an eighth period to the table. This begs the question: how much further can the table be extended? This is where Witek Nazarewicz grabbles with the intricacies of chemical theory.
As he writes on the MSU website: “We don't know what they look like, and that's the challenge. But what we have learned so far could possibly mean the end of the periodic table as we know it."
It isa uncertain by how much the periodic table can be extended, in terms of the discovery of new elements. Some scientists are of the view that there is no limit; whereas other researchers think there is a point after which atoms cannot become any heavier. This is because such atoms of an increasing size would be too unstable.
The research is published in the journal Nature, with the paper titled “The limits of nuclear mass and charge.”
Essential Science
Water from the tap
Water from the tap
This article is part of Digital Journal's regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week we looked at a new compound called ‘f-sand’, which has a botanical component. The material has the potential to be used a means to provide clean water to low income countries.
The week before we considered a new study into sodium levels and diet, which indicated that there is a clear association with sodium levels and disease. The new research sends out a new warning.
More about Chemistry, Periodic table, Science, Physics, Elements
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