Nihonium (Nh), a synthetic element with the atomic number 113, is classified as a superheavy element and belongs to Group 13 of the periodic table, placing it directly below thallium. Named after the Japanese word for Japan, “Nihon,” it is entirely man-made. It is impossible to view Nihonium directly in bulk, as only a minuscule number of atoms have ever been created in a laboratory setting. This extreme scarcity and inherent instability preclude observing a visible sample.
Why Nihonium Cannot Be Seen
The physical limitations preventing direct observation stem from Nihonium’s extreme radioactivity and transient nature. As a synthetic element, it is produced atom by atom in specialized facilities, never accumulating into a visible mass. The instability of the atomic nucleus causes created atoms to rapidly undergo radioactive decay.
The most stable known isotope, Nihonium-286, has a half-life of only ten to twenty seconds, while other isotopes decay in milliseconds. This extremely short lifespan means that even if a sample could be amassed, it would instantly disappear. The rarity of its production, coupled with rapid decay, ensures Nihonium remains purely a subject of nuclear physics and theoretical chemistry.
Observing the element requires a bulk quantity of material large enough to interact with light. Since Nihonium atoms are short-lived and few in number, they do not remain long enough to form the crystal lattice or metallic structure necessary for a bulk appearance. Experiments must rely on “atom-at-a-time” chemistry, tracking single atoms as they decay.
How Nihonium is Created and Detected
The creation of Nihonium requires immense energy and precision, typically achieved using powerful particle accelerators. One primary method involves a “cold fusion” reaction, where a beam of lighter, accelerated nuclei is fired at a heavier target nucleus. For instance, scientists at the RIKEN institute in Japan synthesized Nihonium by bombarding Bismuth-209 with a beam of Zinc-70 ions.
The vast majority of collisions fail to produce the desired element, making the process highly inefficient and explaining the rarity of Nihonium atoms. When a successful fusion occurs, the resulting nucleus, Nihonium-278, is highly energetic and must shed this energy to stabilize, often by emitting neutrons. A second method involves the alpha decay of a heavier element, Moscovium (Element 115), which is created by colliding Americium-243 with Calcium-48 ions.
Since direct observation is impossible, scientists confirm the existence of Nihonium by detecting its unique radioactive decay chain. The newly formed Nihonium atom is passed through a separator, like the Gas-filled Recoil Ion Separator (GARIS), which filters it from the initial reactants. As the Nihonium atom decays, it emits alpha particles, transforming into a series of lighter daughter elements, such as Roentgenium, Meitnerium, and Bohrium. The characteristic energy and timing of these sequential decay products act as a distinct fingerprint, confirming the original creation of Nihonium.
Predicted Properties and Relativistic Effects
While no visible sample exists, Nihonium is theoretically predicted to be a post-transition metal and a solid at room temperature, resembling its lighter Group 13 counterparts like Thallium. Its theoretical density is estimated to be very high, potentially 16 to 18 g/cm³, making it far denser than Thallium. If it could be seen, it might possess a metallic luster, though its intense radioactivity would likely cause it to glow due to the ionization of surrounding air.
The element’s predicted chemical behavior is significantly altered by powerful relativistic effects, which arise from the high speed of electrons in its large atomic structure. In heavy atoms like Nihonium, the inner electrons travel at a substantial fraction of the speed of light, causing their mass to increase and their orbitals to contract. This contraction stabilizes the innermost s- and p-orbitals, which profoundly influences the element’s chemistry.
Relativistic effects cause Nihonium to deviate from the simple periodic trends of Group 13 elements. While Group 13 elements typically favor a +3 oxidation state, theoretical models suggest Nihonium will be more stable in the +1 oxidation state, similar to Thallium. The chemical properties of Nihonium are therefore not a simple extrapolation of elements above it, but a unique blend of metallic characteristics influenced by this extreme physics.