The periodic table contains 118 officially recognized chemical elements, ranging from hydrogen, the lightest element, to oganesson, the heaviest element currently recognized. Each element is defined by the number of protons in the nucleus of its atoms, a quantity known as its atomic number.
These 118 elements form the foundation of chemistry. They include the substances that make up living organisms, the gases in Earth’s atmosphere, the metals used in buildings and electronics, and the rare elements found in specialized scientific equipment. Although the periodic table appears complete at 118 elements, scientists continue to investigate whether additional elements can exist.
What determines how many elements exist?
An element is a pure chemical substance whose atoms all have the same number of protons. Hydrogen has one proton, helium has two, and lithium has three. Changing the number of protons changes an atom into a different element.
The number of protons is called the atomic number, and it determines an element’s position on the periodic table. Hydrogen has atomic number 1, while oganesson has atomic number 118. Each successive element has one more proton than the previous one.
Atoms of the same element can have different numbers of neutrons. These variations are called isotopes, but they do not count as separate elements. For example, carbon-12 and carbon-14 are both carbon because each has six protons, even though they contain different numbers of neutrons.
This distinction explains why the periodic table counts elements rather than individual types of atoms. Many isotopes exist, but each belongs to an element determined by its proton count.
How the periodic table is organized
The periodic table arranges elements by increasing atomic number, but its structure also reveals recurring patterns in their chemical properties. These patterns arise largely from the arrangement of electrons around atomic nuclei.
The horizontal rows are called periods, and the vertical columns are called groups. Elements in the same group often behave similarly because their outermost electrons, which participate in chemical reactions, have comparable arrangements.
For example, lithium, sodium, and potassium belong to the same group. These metals react readily with water, although their reactivity differs. Helium, neon, and argon belong to another group known for its low chemical reactivity under ordinary conditions.
The table’s familiar shape reflects how electrons occupy different energy levels and regions around an atom’s nucleus. As atomic numbers increase, electrons fill these regions in a recurring pattern, producing the periodic trends that give the table its name.
The 118 recognized elements occupy seven periods. The table also includes four major regions, commonly called blocks, based on the types of atomic orbitals being filled by electrons. Together, these organizational features help scientists predict chemical behavior and understand relationships among elements.
Are all 118 elements found in nature?
No. Some elements occur naturally on Earth, while others have been produced primarily or exclusively through human experiments.
Many familiar elements occur naturally, including oxygen, carbon, iron, silicon, and gold. Some exist as relatively stable, long-lived atoms, while others are present in radioactive forms that gradually decay into other nuclei.
Technetium, with atomic number 43, was the first element to be produced artificially, although scientists later identified tiny amounts of it in natural materials. Promethium, atomic number 61, is also extremely rare in nature. Both are radioactive.
Elements beyond uranium, atomic number 92, are generally called transuranium elements. Most are produced artificially by nuclear reactions, although extremely small natural quantities of certain transuranium elements can occur under particular conditions.
Scientists create many of these elements by directing accelerated ions or atomic nuclei at target materials. When two nuclei collide with sufficient energy, they may fuse, forming a heavier nucleus. The resulting nucleus can then be identified through its radioactive decay and other measurable properties.
Producing a new element is difficult because positively charged nuclei repel one another. Even when a collision overcomes that electrical repulsion, the nuclei may fail to fuse or may form a nucleus that breaks apart almost immediately.
As a result, some superheavy elements have been detected in only a few atoms. Their existence can be established through carefully measured decay patterns, even when the atoms survive for only a fraction of a second.
Who decides which elements belong on the periodic table?
The International Union of Pure and Applied Chemistry, commonly known as IUPAC, works with the scientific community to establish internationally accepted standards for naming and classifying chemical elements.
Discovering a potential new element requires more than producing an unusual signal in an experiment. Scientists must gather convincing evidence that a nucleus with a previously unconfirmed proton number was created. Because superheavy nuclei decay rapidly and experiments can be difficult to reproduce, evaluating the evidence can take considerable time.
Once a discovery meets the accepted scientific criteria, the researchers responsible may be invited to propose a name and symbol. The proposed name goes through an official review process before it becomes accepted.
The four most recently named elements that completed the table’s seventh period are nihonium (Nh, 113), moscovium (Mc, 115), tennessine (Ts, 117), and oganesson (Og, 118). Their names were formally approved in 2016.
Oganesson occupies the final position on the currently recognized periodic table. Its atomic number, 118, means its nucleus contains 118 protons. This does not necessarily mean it is the heaviest element that could ever exist; it means that no element with a higher atomic number has yet been officially established and added to the table.
Why scientists are searching for element 119 and beyond
The search for new elements is driven by a fundamental question: How far can the periodic table extend before atomic nuclei become too unstable to exist?
As atomic nuclei gain protons, their positive electrical charges create increasing repulsion. The strong nuclear force holds protons and neutrons together over very short distances, but the balance between this attractive force and electrical repulsion becomes increasingly difficult to maintain in very heavy nuclei.
Many superheavy nuclei therefore decay quickly through processes such as alpha decay, in which a nucleus releases a particle containing two protons and two neutrons, or spontaneous fission, in which it splits into smaller nuclei.
However, nuclear theory predicts that certain combinations of protons and neutrons may be more stable than their neighbors. This possibility is known as the island of stability. It does not imply that these nuclei would necessarily be stable indefinitely; some might simply survive longer than other superheavy nuclei.
Scientists are investigating whether elements with atomic numbers 119 and 120 can be produced and whether their properties will match theoretical predictions. Creating them requires challenging experiments, and success is not guaranteed. Even if a new element is produced, researchers must establish its identity before it can be formally recognized.
The eventual upper limit of the periodic table remains uncertain. Nuclear physics provides ways to investigate the question, but no universally established final element number is known.
Why the number of elements matters
Knowing the number of elements helps scientists describe the material world using a consistent chemical framework. Every ordinary chemical substance is built from atoms of one or more elements, and the properties of those atoms determine how substances form and behave.
Hydrogen and oxygen combine to form water. Carbon forms the structural backbone of the molecules essential to life. Silicon is central to modern semiconductor technology, while iron is important in steel production and many biological processes. Rare elements have specialized roles in magnets, electronics, medical applications, and scientific instruments.
The periodic table also helps researchers discover relationships that are not obvious from looking at individual elements. Similar electron arrangements can lead to similar chemical behavior, allowing scientists to make informed predictions about elements that are difficult to study directly.
At present, the answer remains 118 recognized chemical elements. That number reflects the elements whose existence has been established and officially accepted, not a proven limit on the possible complexity of matter. Future experiments may extend the table, revealing new nuclei and providing further insight into the forces that hold atomic matter together.
