The periodic table is a foundational organizational tool in chemistry and physics, providing a structured map of the matter that makes up the universe. Its arrangement systematically groups atoms based on shared chemical behaviors, allowing scientists to predict the properties of elements they have not yet encountered. This dynamic chart reflects our evolving understanding of matter, meaning the total count of known elements increases with scientific advancement and discovery. The table organizes these fundamental substances, ranging from the lightest gases to the heaviest, lab-created metals.
The Current Official Count
There are currently 118 chemical elements that have been officially identified and confirmed. This number completes the seventh horizontal row, known as Period 7, of the modern periodic table. All 118 positions on the chart now hold an element with a recognized name and symbol.
Only 94 of these elements occur naturally on Earth. The remaining 24 elements have been synthesized in laboratories through complex nuclear processes. The inclusion of these artificially created elements reflects decades of research into the limits of atomic structure.
Defining an Element: The Atomic Number
The scientific definition of a chemical element rests entirely on its atomic number. This number is simply the count of protons found within the nucleus of an atom. The atomic number acts as a unique identifier for every element.
If an atom has six protons, it is carbon, and if it has seven protons, it is nitrogen; a change in the proton count fundamentally transforms the atom into a different element. This characteristic is distinct from the number of neutrons, which can vary to create different isotopes of the same element. It is also different from the number of electrons, which can be gained or lost to form charged ions. The proton count, fixed in the nucleus, determines the electron configuration and the atom’s chemical behavior.
The Role of Synthetic Elements and Discovery
The elements with atomic numbers greater than 92, which is the atomic number of uranium, are generally classified as synthetic, or transuranium, elements. These elements do not exist naturally on Earth in substantial quantities and must be created through human manipulation of atomic particles. Scientists create these superheavy elements by using particle accelerators to induce nuclear fusion.
This process involves accelerating a beam of lighter ions, such as calcium, and smashing them into a target made of a heavy element. If the collision is successful and the nuclei fuse, a new, heavier element is formed, often for only a fraction of a second. These newly formed, highly unstable nuclei exist for extremely short half-lives, sometimes lasting only microseconds before decaying.
The discovery of these elements is confirmed by meticulously analyzing the decay chain—the sequence of particles emitted as the element breaks down. Because production is so challenging, researchers often confirm the existence of a new element by observing only a handful of atoms. The instability of these heaviest elements suggests a physical limit to the number of elements that can exist.
How New Elements Are Named and Verified
Before a new element is officially added to the periodic table, its discovery must undergo a rigorous verification process. This validation is performed by a joint working group from the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP). This group examines the experimental evidence to confirm that the element was indeed created and its atomic number correctly identified.
During the verification period, the element is assigned a systematic, temporary name based on its atomic number, using numerical roots. Once the discovery is confirmed and credit is assigned to the laboratory, the discoverers are invited to propose a permanent name and a chemical symbol to the IUPAC Inorganic Chemistry Division.
IUPAC rules stipulate that an element can be named after a mythological concept, a mineral, a geographical location or country, a property of the element, or a scientist. After a public review period, the IUPAC Council gives the final approval, making the new element’s name and symbol official.