Explore a nuclide chart, which displays every known isotope, how it's most likely to radioactively decay, and the 'band of stability' for all known elements.

Unusually stable, undiscovered elements may exist near atomic number 126

While heavier elements like uranium and plutonium are unstable and decay quickly, simulations suggest a pocket of stability exists for elements with approximately 126 protons and 184 neutrons. Such elements may have practical applications, such as americium, a synthetic element used in smoke detectors.

Build atomic nuclei to explore their instability and resulting radioactive decay

In this simulation, users can add protons and neutrons to create an atomic nucleus, view its half-life and decay options, and identify patterns in how specific combinations of particles create extremely stable nuclei, from which the nuclear shell model of stability emerged.

View the periodic table of radioactive elements, and a list of each's most stable isotopes

Technetium is the lightest artificial radioactive element, which is produced primarily as a byproduct of nuclear fission. Several unstable isotopes are commercially available to medical professionals and scientists, despite their radioactivity risks.

How the nuclear shell model explains the stability or radioactivity of atomic nuclei

When the number of protons and neutrons completely fills shells within the nucleus, the binding energy that prevents these particles from being pulled apart increases. These are called "magic numbers," and they produce atoms with exceptionally stable nuclear configurations.

An overview of radioactivity, which can spontaneously change one element into another

Unstable atomic nuclei can transmute into a new element—an atom with a different number of protons—by emitting an alpha particle (two protons and two neutrons) or a beta particle (an electron). The electron can emerge from the nucleus when a neutron, which has no charge, suddenly transforms into a proton and an electron, thereby maintaining zero charge before and after the transformation, but altering the original element.

With less than 50 milligrams present in the top kilometer of Earth's crust at any given time, astatine is the rarest naturally occurring element on the planet.

Scientists can determine the age of rocks, fossils, and other ancient samples by measuring how many radioactive atoms in the sample have decayed, a process that occurs at precise, well-known rates.

An explanation of isotopes, which can help scientists trace food, water, and farming choices

Atoms of the same element have the same number of protons, but experiments showed that atoms of the same element can move through electromagnetic fields as if they had different masses. These differences in mass come from variations in the number of neutrons, which contribute to the stability of atoms by providing a buffer to the repulsion between protons.

Watch a visualization of a fission chain reaction

When a neutron collides with an atom, it is absorbed into the nucleus. If the resulting nucleus is unstable, it can undergo a series of decays that turn it into a less massive nucleus while releasing energy and other particles.

View summaries of the most common types of radioactive decay and their associated particles

The alpha particle has the strongest ability to ionize other atoms it strikes, but it also does not travel very far before colliding with something and being absorbed. Gamma particles—high-energy photons—do not interact with matter as easily and therefore possess the greatest penetrating power, though this also makes their ionizing potential the smallest.

Less common types of radioactive decay include emitting neutrons and antimatter

Through neutron emission, one or more neutrons are ejected from atoms that have far fewer protons. Neutrons can also be released by artificially inducing the fission, or separation, of a large atomic nucleus into smaller ones. During beta-plus decay, a positron—the antimatter version of an electron—is produced when a proton turns into a neutron.

Besides the periodic table, there are over 1,000 alternative ways to organize the known elements, with many arrangements emphasizing specific trends among them.

View the evolution of atomic models, with four successively overturned between 1900 and 1926

Originally thought to be indivisible spheres unique to each element, the discovery of the electron by J.J. Thomson revealed them to be made of smaller particles. Ernest Rutherford's gold foil experiment uncovered the existence of nuclei, which Niels Bohr suggested were surrounded by electrons in fixed orbits. By applying quantum mechanics, Erwin Schrödinger replaced orbits with probability clouds.

Fusion reactions and radioactive decay produce elements inside stars

Hydrogen, present since the early universe, serves as fuel for the proton-proton chain, producing helium, which is then incorporated into the CNO cycle to produce carbon, nitrogen, and oxygen. Additional fusions of helium with these elements and subsequent decays via the alpha ladder produce elements up to iron and bismuth.

Simulate the decay of a radioactive substance to visualize its half-life

By definition, the half-life is the amount of time it takes for half of a radioactive sample to decay. With each half-life that has elapsed, half of the starting sample is left, leaving less to decay each time. This results in the number of undecayed atoms decreasing exponentially, with less stable substances having shorter half-lives and decreasing exponentially more rapidly.

View a ranking of the masses of fundamental particles, from the massless photon to the top quark, and a timeline of their discoveries.

The world's first artificial element, technetium, was discovered 68 years after its existence was predicted in order to fill a gap in the periodic table.

An explanation of the weak nuclear force, which can induce some forms of radioactive decay

While the strong nuclear force holds the protons and neutrons together in an atomic nucleus, despite the electromagnetic force pushing protons apart, the weak nuclear force can change the identity, or flavor, of the quarks that make up these particles. In doing so, protons can be converted into neutrons, and vice versa, altering the stability of atomic nuclei.

Elements, isotopes, and ions can be identified by the number of protons, neutrons, and electrons within the atoms that make up a substance.

Explore an interactive periodic table of each element's history, properties, and uses.

How scientists determine elemental composition based on the light emitted by cooling atoms

When electrons within an atom drop to a lower energy level closer to the nucleus, they lose energy and produce light with energy equal to the difference between the two energy levels. Because these levels and the corresponding emitted light are unique to each element, the light serves as a unique signature that can be compared to known lab samples for identification.

Visualizing the chemistry of nuclear weapons

Nuclear weapons have devastating effects, but the science of how they work is atomically small. There are two main types of nuclear reaction: fission and fusion. The fission bomb produces immense energy by splitting an atom, the result of firing a...

The periodic table organizes elements by atomic structure and common properties

Developed by Dmitri Mendeleev in 1869, the arrangement places elements into columns, called groups, if they share the same number of electrons in their outer shell, indicating similar chemical behavior. From left to right across rows, or periods, elements have more protons, as well as corresponding electrons when neutral.

Visualize what happens to atoms during nuclear fission and how the process produces energy

Nuclear fission occurs when an unstable, often massive, atomic nucleus splits into smaller ones—daughter atoms—and releases energy. Within a nuclear reactor, these daughter atoms can collide and combine with neighboring atoms, destabilizing them and triggering a chain reaction of atomic splitting.

By organizing elements by atomic weight, Dmitri Mendeleev created the periodic table

The organization included groupings based on similar chemical properties and patterns in atomic weights. This left gaps that were used to predict the properties of elements yet to be discovered—including germanium and gallium—with high accuracy.

The outermost shell of electrons in an atom dictates how it bonds to other atoms, including those of the same element, and the properties of the materials composed of those atoms.

An overview of helium, the nonrenewable resource that's lighter than air

The second element in the periodic table naturally forms deep underground over the course of billions of years through the decay of radioactive elements, but it is used and lost to space at rates faster than it is generated. Because of this and its extensive applications in scientific technologies, scientists continue to seek avenues for its exploration, storage, and recycling.

View the most expensive materials on Earth, led by antimatter and other elements forged in particle accelerators.

Helium formation, from radioactive decay inside Earth to nuclear fusion within stellar cores

Over the course of billions of years, uranium and thorium undergo alpha decay, producing helium nuclei—two protons and two neutrons—which become helium atoms after gaining two electrons. This helium becomes trapped in underground reservoirs along with other gases and can be recovered during natural gas extraction.

Nuclear batteries generate electrical currents using radioactive materials

Rather than using electrochemical reactions to produce the electrons that flow through a circuit, isotopes like nickel-63 undergo beta decay—emitting electrons—which a semiconducting material can absorb to establish a charge imbalance that generates current. Such batteries could provide low-power energy for decades.

While both are nuclear weapons, atomic bombs release nuclear energy by splitting large atomic nuclei, whereas hydrogen bombs derive most of their energy from fusing heavy hydrogen isotopes.

Build atoms to learn about atomic number, mass number, and charge notations

In this simulation, users can add protons, neutrons, and electrons to create atoms, view their stability and atomic configurations, and identify how the amounts of these subatomic particles are detailed around the abbreviation for the resulting element using AZE notation.

View a step-by-step breakdown of how helium is forged in stars alongside antimatter

During the proton-proton chain, four hydrogen nuclei—protons—are fused together to create an alpha particle—a helium nucleus—and produce the energy that supports a star's own weight. Through radioactive decay, two of these protons become neutrons, with each releasing an antielectron, or positron, and an electron neutrino.

Although they rely on radioactive elements to operate, everyday technologies such as electronic exit signs, some wristwatches, and smoke detectors are not dangerous, unless they are damaged and their radioactive material is inhaled or swallowed.

Why most atoms do not spontaneously break apart, despite protons repelling one another

At small scales, the strong nuclear force overwhelms electromagnetic repulsion between positively charged particles, keeping the nucleus intact. However, because the force's range is limited, it cannot provide the attraction needed to hold onto protons that are spread out across very large atomic nuclei.

Cosmogenic nuclide dating reveals how long a surface has been exposed to air by measuring the abundance of rare isotopes produced when cosmic rays interact with minerals.

The history of the periodic table and how it hinted at atoms possessing internal structure

In 1869, more than two decades before the discovery of electrons, Russian chemist Dmitrii Mendeleev organized known elements by atomic weight and chemical properties using index cards. His organization revealed previously undiscovered elements and identified patterns in the reactivity of elements, which would later be linked to each element's outermost electron shell. (Some readers may experience a paywall.)

The strong nuclear force, which keeps atomic nuclei intact, is mediated by gluons—massless particles that bind together the quarks that make up protons and neutrons.

Uranium's ability to split easily makes it the most common catalyst for nuclear power

Uranium is commonly found in rocks, water, and soil worldwide, but significant industrial processes are needed to process and enrich it for efficient reactor usage. After being irradiated in reactors, it must be cooled down before disposal.

Items in the Curie Museum do not produce significant radioactivity today

Ionizing radiation produced by elements such as uranium, polonium, and radium can damage living things, but the trace amounts found in the museum objects that Marie Curie once touched have been largely decontaminated, with more dangerous items stored in protective, lead-lined containers.

A look inside neutron stars, which are thought to contain nuclear pasta

Simulations show that beneath the outer crust of these objects, the gravitational force is so extreme that atomic nuclei link together into chains of primarily neutrons and some protons called nuclear spaghetti. Deeper in the star, these links combine to form sheets—nuclear lasagna—a quintillion times stronger than steel, making it the strongest material in the universe.

Learn about ionizing radiation and see the most radioactive places on Earth

The average person is exposed to radiation every day, though most of it is either harmless non-ionizing radiation or ionizing radiation at doses too small to significantly affect an individual. The highest doses of ionizing radiation are received by smokers due to the radioactive polonium and radioactive lead in tobacco products.

How radioactive isotopes are created and used for medical diagnostics

In particle accelerators, protons can be accelerated into other atoms to create radioactive isotopes, which can be attached to specific molecules to create radiotracers that are taken up by specific cells. Radiotracers can emit particles that produce light once they collide with an electron, and this light can be captured by a PET scanner to diagnose specific ailments.

Methods for disposing of nuclear waste include melting it into a liquid to create glass, dumping it into graphite blocks, storing it in lead-lined rooms, and submerging it in deep pools of water.

The different energy levels of each element result in unique colors when burned

When heated, electrons absorb energy and move to excited states within an atom. They promptly drop back down and release light energy corresponding to the size of the drop, which is unique to each element.

The average banana produces one positron—the antimatter counterpart to an electron—every 75 minutes as its trace amounts of radioactive potassium decay.

How gold, platinum, and many rare earth elements form during neutron star mergers

While massive stars naturally fuse elements as heavy as iron, an analysis of gravitational waves from the collision of two neutron stars revealed that more massive elements are created in this environment via rapid neutron capture—the r-process. This phenomenon sees existing iron nuclei absorb plentiful free neutrons, many of which decay into protons, creating new elements.

Nuclear power relies on chain reactions involving uranium-235, but because the isotope's concentration in natural ores is too low to sustain these reactions, enrichment is needed to produce more highly concentrated fuel.

Gravity, electromagnetism, and two nuclear forces make up nature’s fundamental forces

While gravity is the most familiar force, it is also the weakest and the only one without a particle to mediate the force. The weak nuclear force is responsible for radioactive decay and transmutation of elements, while the strong nuclear force holds quarks together.

An overview of atomic composition, scale, and structure, which is almost all 'empty' space

It takes about 500,000 carbon atoms lined up next to one another to span the thickness of human hair, and over 99.9994% of the mass of each is contained in the nucleus. About 99.999999999999% of an atom's volume lies outside this nucleus, where electrons exist in clouds of probability. Removing these clouds, the Empire State Building would be the size of a rice grain.