The periodic table lists 118 different types of atoms that form all matter. While many elements exist naturally on Earth, the heavier ones often do not. Scientists artificially create these missing elements by manipulating the fundamental building blocks of matter in specialized facilities. These elements, first produced in a laboratory and not occurring in substantial quantities in nature, are known as synthetic or artificial elements.
Defining Synthetic Elements
Synthetic elements are defined by having an atomic number greater than 92, the atomic number of the heaviest naturally occurring element, uranium. This classification is referred to as the transuranic elements, meaning “beyond uranium.” These elements are heavier than uranium and are all unstable, which is why they are not found in the Earth’s crust today.
The first few transuranic elements, such as neptunium (atomic number 93) and plutonium (atomic number 94), were first synthesized in a laboratory setting. They are sometimes found in trace quantities in concentrated uranium ores, resulting from natural processes like neutron capture and subsequent radioactive decay. However, all elements with an atomic number of 95 or higher are considered purely synthetic, having been discovered and produced exclusively by human intervention.
The Physics of Element Creation
Creating a new, heavier element involves overcoming the immense electrical repulsion between atomic nuclei. Scientists accomplish this using specialized machines known as particle accelerators, sometimes referred to as atom smashers. These devices accelerate a beam of lighter, positively charged nuclei (the “projectile”) to speeds approaching a fraction of the speed of light. This high velocity is necessary to penetrate the electron clouds and overcome the repulsive force of the target nucleus.
The projectile beam is directed at a thin foil made of a heavy target element, such as Californium or Berkelium. This process is essentially nuclear fusion, where the nuclei of the projectile and the target momentarily combine to form a single, heavier nucleus. For example, Oganesson (element 118) was created by firing a stream of Calcium-48 nuclei at a target of Californium-249. Most high-speed collisions result in the nuclei fragmenting or flying apart, making the successful fusion event that creates the new element extremely rare.
The successful creation of a new element is a singular, fleeting event that requires highly specialized detection equipment to confirm. Researchers must analyze the decay chain of the new nucleus to confirm its atomic number and identity. This complex production method explains why these elements are only produced in microscopic quantities at highly advanced scientific facilities.
Instability and the Island of Stability
A defining characteristic of synthetic elements is their instability, causing them to decay rapidly through radioactivity. This instability is quantified by an element’s half-life, the time required for half of the original atoms to decay into lighter elements. For the heaviest synthetic elements, this half-life can be incredibly short, sometimes lasting only milliseconds before the atom spontaneously breaks apart. This rapid decay is a direct consequence of the overwhelming repulsive force between the high number of protons packed into the nucleus.
Despite the general trend of decreasing stability with increasing atomic number, nuclear physics theory predicts a region of relative stability called the “Island of Stability.” This is a theoretical grouping of superheavy isotopes expected to have a structure that grants them significantly longer half-lives. The predicted stability is based on the nuclear shell model, which suggests that atoms with specific “magic numbers” of protons and neutrons form closed, more stable nuclear shells.
Scientists are focused on synthesizing superheavy elements that possess the neutron and proton counts necessary to reach this island. While most superheavy elements decay in fractions of a second, isotopes located on the Island of Stability are theorized to have half-lives ranging from minutes or hours up to millions of years. Reaching this predicted region would allow researchers to study the chemical properties of these elements in detail, which is currently impossible due to their extreme brevity.