How the number of subatomic particles helps identify different types of atoms

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.

Understanding how atomic structure contributes to each element's properties

The outermost layer of electrons in an atom dictates how it will bond to other atoms. These bonds determine whether elements exist as solids, liquids, or gases in the environment and other characteristics. For example, electrons are freely shared between atoms in metallic bonds, allowing them to immediately re-emit light that strikes them, thus making most metals shiny.

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.

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.

Ernest Rutherford's gold foil and nitrogen experiments revealed nuclear structure

Observing high-angle deflections when alpha particles were fired at gold foil led to an atomic model with a dense, positively charged nucleus. Firing those particles at nitrogen resulted in the emission of hydrogen nuclei—protons—leading to the discovery of the subatomic particle.

Distinguishing polar and nonpolar molecules and why charges get distributed unevenly in molecules

Because each element has a unique number of protons and configuration where electrons exist, they attract electrons that are shared with other elements in chemical bonds to varying degrees. When this attraction—electronegativity—varies between two bonded elements, electrons are more likely to be near the more electronegative element and away from the less electronegative element. This can create regions of opposite charge, or poles, and thus polar molecules.

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.

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.

The features of neutrinos, the second most abundant particles in the universe

Fundamental particles produced during nuclear interactions, such as those within stars and particle accelerators, neutrinos have almost no mass, rarely interact with other particles, and come in three varieties, or flavors. Each type can change into the others as it travels through space, a process called neutrino oscillation.

The quark model helps organize hundreds of discovered particles

All isolated matter particles are either leptons, like the electron, or composed of combinations of six different flavors of quarks. Quarks introduced flavor quantum numbers—physical quantities possessed by specific quarks whose total value must be conserved in all particle interactions.

How atomic clocks have been used to measure the universe's fundamental constants

Atoms behave according to a set of parameters that scientists have determined give reality its properties. For example, the fine-structure constant, α, quantifies the strength of interactions between charged particles. Since the light emitted by atoms as they move between energy levels is affected by α, analyzing these emissions—the basis of atomic clocks—using different atoms helps calculate α.

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.

The one-electron theory describes the universe as having only one electron

The thought experiment explains why every electron has the same charge and mass as every other electron, and describes every positron—the antimatter version of the electron—as that same electron traveling backwards in time. Among other foundational challenges, the model suggests that the universe contains equal numbers of electrons and positrons, yet normal matter is much more common than antimatter.

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.

Particle accelerators detect subatomic particles using millions of sensors

Calorimeters measure the energy of particles. Tracking devices can measure momentum and charge from the trajectory of particles, which is determined by recording tiny electrical signals. Time-of-flight detectors provide particle velocities directly and particle mass indirectly, giving physicists a suite of properties to compare with those of known matter.

The deceptively simple proton

Take a visual deep-dive into the proton, a near-fundamental—but deceivingly simple—building block of nature. Among other beguiling characteristics, the particle can't be described by its constituent particles (quarks), but rather exists in a...

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.

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.

Explaining the unified atomic mass units, which quantifies the mass of atoms and molecules

Until 1961, the atomic mass unit was defined based on oxygen-16, but it was later replaced by the unified atomic mass unit, defined as 1/12th the mass of a carbon-12 atom. Today, the term "atomic mass unit" often refers to the "unified atomic mass unit," denoted by the symbol u.

Why quantum mechanics causes disagreement on where the edge of an atom is located

The quantum model of the atom describes it as having a dense nucleus at its center, surrounded by electrons in probability clouds where they are most likely to be found. The fundamental uncertainty of these clouds has led to various methods and resulting measurements of the atomic radius. (Some readers may experience a paywall.)

Measurements of an electron’s magnetic moment help test the Standard Model

A particle’s magnetic moment quantifies how it responds to the presence of an external magnetic field. An electron’s value can be measured down to 14 decimal places, with certainties in the first 12 allowing it to be used to assess the accuracy of predictive models.

Nitrogenous bases connect like puzzle pieces due to their shape

There are four bases—adenine, thymine, cytosine, and guanine—which keep the two strands of DNA connected via chemical bonds between them. Connections between thymine and adenine require two hydrogen bonds, while those between cytosine and guanine need three hydrogen bonds. These differences in bond number prevent non-complementary pairings.

Why the ratios of helium isotopes are analyzed to investigate ocean circulation

Volcanic activity on the seafloor produces high ratios of helium-3 to helium-4, which can be tracked in ocean samples more easily than other elements because helium is nonreactive. Water from deep ocean currents can also be distinguished from air-exposed surface water sources by comparing these ratios, since atmospheric helium ratios are much lower.

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.

About 99% of Earth's atmosphere is made of nitrogen and oxygen

At 78% and 21% respectively, the two elements are followed by argon with almost 1%. Trace amounts of other molecules, including greenhouse gases such as methane and carbon dioxide, and particulate matter such as dust and pollen, make up the remainder of the atmosphere's contents.

The complexity of classifying a tree

It may seem obvious to us when we see a tree, but very specific characteristics cause scientists to distinguish trees from other types of plants. This video provides a visual and verbal explanation of distinctions that separate trees from other plants like shrubs or herbs. See a scientific breakdown of these traits.

Explore the abundance of different types of cells in the human body

Lacking a nucleus and other organelles to maximize space for oxygen-carrying hemoglobin and enhance maneuverability through narrow capillaries, there are about four times as many red blood cells and platelets as all other cell types in the body combined. However, about half of the body's cell biomass consists of skeletal myocytes, or muscle fibers.

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

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

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

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

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.

Stars appear to twinkle because turbulence in the motion of molecules in Earth's atmosphere causes light to bend and wiggle rapidly on its way to the surface—a phenomenon called scintillation.

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

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.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

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

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

The Nasdaq's 'Magnificent 7' companies are responsible for roughly 40% of the Nasdaq 100 index's gains, while the remaining 93 companies account for the other 60%.

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

This poison ivy knowledge quiz—accompanied by photos of the plant's varied forms—may help you identify this common rash-inducing growth.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

Corals are themselves not coral reefs—the term refers to the tiny marine invertebrates that build the rigid reef.

Some researchers have labeled nomophobia, the fear of being without your phone, as 'the phobia of the 21st century.'

Meet the 56 signers of the Declaration of Independence—most of whom didn't put pen to paper until August 2, 1776—and see their original signatures.

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

Ebola is a filovirus, meaning it resembles a thread under a microscope, though it sometimes twists and can resemble a bowl of spaghetti.

A pickleball's loud 'pop' sound can reach 120 decibels, which is equivalent to a hammer hitting a nail

The identity of the Tank Man in the iconic photo from the 1989 Tiananmen Square protests remains unknown and was possibly killed.