Nihonium

Nihonium is a synthetic chemical element with the symbol Nh and atomic number 113. It is extremely radioactive, with its most stable known isotope, nihonium-286, having a half-life of about 10 seconds. Nihonium is a transactinide element in the p-block of the periodic table, located in period 7 and group 13.

Nihonium was first reported to have been created in experiments between July and August 2003 by a Russian–American team at the Joint Institute for Nuclear Research in Dubna, Russia, and later confirmed by a Japanese team at Riken in Wakō, Japan in 2004. The confirmation involved many independent teams around the world. In 2015, the IUPAC/IUPAP Joint Working Party recognized the discovery and gave naming rights to the Riken team, who proposed the name nihonium in 2016, which was approved the same year. The name comes from the common Japanese name for Japan, Nihon.

Very little is known about nihonium because it has only been made in tiny amounts that decay quickly. It is expected to behave similarly to elements like boron, aluminium, gallium, indium, and thallium, but with some important differences, such as being more stable in the +1 oxidation state. Early experiments suggest that nihonium is less reactive than thallium and not very volatile.

Introduction

Nihonium is a special kind of element that scientists create in laboratories. It has the symbol Nh and the number 113, which tells us its place among all the elements. This element is very unstable and breaks down quickly — the longest-lasting version only stays around for about 10 seconds before it changes. Nihonium belongs to a group of elements called transactinides, which are found in the outer part of the periodic table of elements.

History

The syntheses of elements were conducted at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, from 1981 to 1996. These elements were made by reactions in which targets made of lead and bismuth, which are around the stable configuration of 82 protons, are bombarded with heavy ions of period 4 elements. This creates fused nuclei with low excitation energies due to the stability of the targets' nuclei, significantly increasing the yield of superheavy elements.

The first report of element 113 was in August 2003, when it was identified as an alpha decay product of element 115. Element 115 had been produced by bombarding a target of americium-243 with calcium-48 projectiles. In 2004, the results were published.

While the JINR–LLNL collaboration had been studying fusion reactions with calcium-48, a team of Japanese scientists at the Riken Nishina Center for Accelerator-Based Science in Wakō, Japan, led by Kōsuke Morita had been studying cold fusion reactions. In 2001, his team confirmed discoveries of elements, and then made a new attempt on element 113. In July 2004, the Riken team detected a single atom of 278113 and published their results that September.

In December 2015, the conclusions of a new JWP report were published by IUPAC, in which element 113 was awarded to Riken. The full JWP reports were published on 21 January 2016. The JWP recognised the discovery of element 113, assigning priority to Riken.

Using Mendeleev's nomenclature for unnamed and undiscovered elements, nihonium would be known as eka-thallium. In 1979, IUPAC published recommendations according to which the element was to be called ununtrium (with the corresponding symbol of Uut), a systematic element name as a placeholder, until the discovery of the element is confirmed and a name is decided on.

Before the JWP recognition of their priority, the Japanese team had unofficially suggested various names: japonium, after their home country; nishinanium, after Japanese physicist Yoshio Nishina, the "founding father of modern physics research in Japan"; and rikenium, after the institute. After the recognition, the Riken team gathered in February 2016 to decide on a name. The name nihonium was chosen after an hour of deliberation: it comes from Nihon, one of the two Japanese pronunciations for the name of Japan. In March 2016, Morita proposed the name "nihonium" to IUPAC, with the symbol Nh. The name was officially approved on 28 November 2016. The naming ceremony for the new element was held in Tokyo, Japan, on 14 March 2017, with Naruhito, then the Crown Prince of Japan, in attendance.

Isotopes

Main article: Isotopes of nihonium

Nihonium does not occur naturally and has no stable forms. Scientists create different versions, called isotopes, of nihonium in labs. These isotopes are all radioactive and break down quickly. The heaviest and most stable one, nihonium-286, lasts about 8 seconds before it changes.

Researchers have made eight isotopes of nihonium with different weights, but some of these have not been fully confirmed. These isotopes break down in various ways, often turning into other elements. Scientists are still studying these isotopes to learn more about their properties and how they might fit into ideas about very heavy elements that could be more stable than expected.

Predicted properties

Very few properties of nihonium or its compounds have been measured. This is because making and studying nihonium is very difficult and expensive, and it breaks down quickly. Most of what we know about nihonium is based on predictions.

Nihonium is the first element in the 7p series and the heaviest element in group 13 of the periodic table. It is found below boron, aluminium, gallium, indium, and thallium. All these elements except boron are metals, and nihonium is expected to be a metal too. Nihonium is predicted to behave differently from these lighter elements because of strong effects caused by how fast its electrons move, which is close to the speed of light.

Nihonium is expected to have an atomic radius about the same as thallium, but it should be much denser. It might melt at around 430°C and boil at around 1100°C. The chemistry of nihonium is expected to be different from thallium because of these strong effects, making nihonium less reactive.

Nihonium is predicted to prefer a +1 oxidation state, similar to thallium, but even more so. Simple compounds like nihonium monohydride (NhH) and monofluoride (NhF) are expected to exist. Nihonium might also show some properties similar to the halogens, like being able to gain an electron to form a -1 oxidation state. Higher oxidation states like +3 and +5 have been suggested for nihonium, but these compounds are expected to be very unstable.

Experimental chemistry

Scientists have studied nihonium, a very rare and radioactive element, to learn about its properties. They made nihonium atoms by mixing special materials and then watched how these atoms moved through special tubes. They found that nihonium did not move through the tubes easily, which surprised them.

In later tests, scientists looked at how nihonium sticks to different surfaces. They discovered that nihonium reacts a little less than a similar element but more than some other nearby elements on the periodic table. This helps scientists understand more about nihonium’s behavior.