Mar 19, 2025 · Atom, smallest unit into which matter can be divided without the release of electrically charged particles. It also is the smallest unit of matter that has the characteristic properties of a chemical element.

atom, Smallest unit into which matter can be divided and still retain the characteristic properties of an element. The word derives from the Greek atomos (“indivisible”), and the atom was believed to be indivisible until the early 20th century, when electrons and the nucleus were discovered.

Explore an atom's interior to discover the layout of its nucleus, protons, and electrons.

An atom is the smallest piece of matter that has the characteristic properties of a chemical element, such as hydrogen, oxygen, calcium, iron, gold, and neon. More than 90 types of atom exist in nature, and each one forms a different element.

An atom is the smallest unit of an element, and each chemical element has a unique atomic number. For instance, hydrogen has an atomic number of 1 because every hydrogen atom has one proton in its nucleus.

atomic physics, the scientific study of the structure of the atom, its energy states, and its interactions with other particles and with electric and magnetic fields.

Mar 19, 2025 · The mass of an atom consists of the mass of the nucleus plus that of the electrons, so the atomic mass unit is not exactly the same as the mass of the proton or neutron. The electron Charge, mass, and spin

Mar 19, 2025 · Atom - Nuclear Shell, Structure, Model: Many models describe the way protons and neutrons are arranged inside a nucleus. One of the most successful and simple to understand is the shell model. In this model the protons and neutrons occupy separate systems of shells, analogous to the shells in which electrons are found outside the nucleus.

Atomic model, in physics, a model used to describe the structure and makeup of an atom. Atomic models have gone through many changes over time, evolving as necessary to fit experimental data. For a more in-depth discussion of the history of …

Mar 19, 2025 · Atom - Electrons, Orbitals, Energy: Unlike planets orbiting the Sun, electrons cannot be at any arbitrary distance from the nucleus; they can exist only in certain specific locations called allowed orbits.