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  1. Atom | Definition, Structure, History, Examples, Diagram, & Facts ...

    4 days ago · However, atoms are made up of three types of subatomic particles: the heavy protons and neutrons that make up the nucleus (the central part of the atom), and the much …

  2. Atomic physics | Structure, Particles & Energy | Britannica

    It attempts to describe and account for the properties of molecules and atoms and their constituents— electrons, protons, neutrons, and other more esoteric particles such as quarks …

  3. Atom - Development, Theory, Structure | Britannica

    Sep 7, 2025 · Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped. …

  4. Atom - Electrons, Protons, Neutrons | Britannica

    Sep 7, 2025 · When he conducted his atomic mass experiments with neon gas, he found that a beam of neon atoms subjected to electric and magnetic forces split into two parabolas instead …

  5. atom - Kids | Britannica Kids | Homework Help

    The tiny particles called atoms are the basic building blocks of all matter. Atoms can be combined with other atoms to form molecules, but they cannot be divided into smaller parts by ordinary …

  6. atom - Students | Britannica Kids | Homework Help

    Atoms are made up of three basic types of particle: protons, neutrons, and electrons. These particles (as well as other particles smaller than atoms) are known as subatomic particles.

  7. Atomism | Definition, Philosophy, History, & Facts | Britannica

    Atomism in the strict sense is characterized by three points: the atoms are absolutely indivisible, qualitatively identical (i.e., distinct only in shape, size, and motion), and combinable with each …

  8. Periodic table | Definition, Elements, Groups, Charges, Trends,

    Sep 18, 2025 · In subsequent years great progress was made in explaining the periodic law in terms of the electronic structure of atoms and molecules. This clarification has increased the …

  9. Chemical bonding - Covalent, Molecules, Atoms | Britannica

    Sep 5, 2025 · Chemical bonding - Covalent, Molecules, Atoms: When none of the elements in a compound is a metal, no atoms in the compound have an ionization energy low enough for …

  10. John Dalton - Atomic Theory, Chemistry, Physics | Britannica

    Oct 21, 2025 · Dalton claimed that atoms of different elements vary in size and mass, and indeed this claim is the cardinal feature of his atomic theory.