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

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.

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.

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.

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.

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.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

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.

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.

Particle accelerators allow physicists to create controlled nuclear experiments

Before the 1930s, scientists relied on naturally radioactive substances to learn about atomic nuclei. The first atom was split in 1932 when John Cockcroft and Ernest Walton fired a beam of accelerated protons at a lithium atom, producing alpha radiation.

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.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

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.

The discovery of the neutron paved the way for nuclear weapons

In 1932, James Chadwick discovered the subatomic particle when trying to explain the radiation emitted by beryllium after it was bombarded with alpha particles. The radiation’s ability to eject protons from a target suggested a chargeless particle with slightly more mass than a proton.

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.

Distinguishing between natural and artificial, or induced, radioactivity

Naturally occurring radioactivity comes from radioactive elements underground, cosmic radiation from the sun and other objects in space, and radioactive atoms that make up the molecules we breathe, eat, and drink. Artificial radioactivity is predominantly generated for medical applications and industrial activities.

A list of five everyday products that rely on radioactivity, including exit signs and gemstones

Like some glow-in-the-dark wristwatches, some exit signs contain sealed tubes of tritium—radioactive hydrogen gas—which emit low-energy beta particles that react with surrounding elements to produce light, making them visible without batteries. In smoke detectors, smoke particles disrupt the steady flow of ions generated by americium-241.

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.

Explaining why solving the solar neutrino problem revealed that neutrinos could transform

Electron neutrinos are byproducts of the nuclear reactions within the sun's core. Based on the sun's energy output, scientists modeled reaction rates and predicted neutrino production, but the observed values were consistently one-third the predicted values. Experiments later showed that these neutrinos could change into other types on their way to Earth, causing the discrepancy.

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.

Radioactivity was accidentally discovered when uranium left marks on photographic plates

In 1896, Henri Becquerel had been exploring phosphorescence—the emission of light of one color after an object is exposed to another color. He expected these emissions to come from objects exposed to sunlight, but he observed emissions after an overcast day.

Scientists turn alchemists, transforming transform lead into gold

Fulfilling alchemists' dreams, scientists at the Large Hadron Collider (LHC) transmute lead into gold. While the 86 billion gold nuclei produced were short-lived, the experiment sheds light on how electromagnetic fields can play a critical role in nuclear transmutation.

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

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.

An imbalance in nuclear reactivity factors caused Chernobyl's reactor to explode

The initial explosion resulted from excessive steam pressure that had built up in a runaway manner due to design flaws and violations of safety protocols. Once exposed to atmospheric oxygen, the hot graphite in the control rods underwent a combustion reaction, resulting in a secondary explosion.

Batteries store energy in chemical bonds that can be turned into electricity

To achieve a more stable, nonreactive state, many elements in nature are reactive and will seek to lose electrons via oxidation or gain electrons through reduction reactions. By pairing an oxidizing chemical with a reducing chemical in a battery, electrons will naturally flow between them, producing an electric current.

How radio works

Antennae tune a radio to a particular frequency (determined by the listener on their radio's dial) while tuning out all the other stations being broadcast. AM, short for amplitude modulation, and FM, short for frequency modulation, decode audio signals differently, leading to differences in sound quality and the distance a station can travel.

Neutron stars, the remains of some massive stars after they explode in a supernova, are the densest directly observable objects in the universe.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

In 1984, Operation Smash Hit intentionally crashed a 239-ton train into a nuclear waste canister at 100 miles per hour to prove the canister's safety, which remained completely intact and lost just 0.29 of its 100 pounds of pressure.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

The history of many kitchen appliances involves unexpected discoveries and applications, including wartime radar turned hamster defroster and replacing an 'ice king' with heat-stealing boxes.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Watch how viruses like Ebola can spill over from animals to humans—and vice-versa.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

When caught in the mouths of cardinal fish, seed shrimp release glowing, bioluminescent chemicals, which alert predators of the cardinal fish, prompting the shrimp's ejection.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

In recent years a child anxiety expert has created and tested a novel phobia and anxiety treatment approach for children, focused on changing how parents respond to the fears.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

The United States has had a tumultuous relationship with Cuba since its 1959 revolution, highlighted by a nuclear crisis and a decades-long trade embargo.

See 33 images that became central to huge scandals, including a young Charles and Camilla, Michael Jackson's baby on a hotel balcony, and Hugh Grant's mugshot.

An initial public offering or 'IPO' is the process of a private company becoming public by putting shares of the company on the stock market for purchase.

Existentialist writer Jean-Paul Sartre coined the famous phrase 'Hell is—other people' in his play 'No Exit'