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

    Sep 7, 2025 · 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. Atomic model | Definition, History, Development, Examples,

    Dalton stated that all atoms of an element are identical in shape, size, and mass. When atoms are involved in chemical reactions, they combine in small whole-number ratios to form what are …

  4. Atom - Development, Theory, Structure | Britannica

    Sep 7, 2025 · Dalton had begun his atomic studies by wondering why the different gases in the atmosphere do not separate, with the heaviest on the bottom and the lightest on the top. He …

  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. Atomic theory | Definition, Scientists, History, & Facts | Britannica

    To the extent that the Schrödinger equation can be solved for more-complex cases, atomic theory is capable of predicting from first principles the properties of all atoms and their interactions.

  8. 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 …

  9. Bohr model | Description, Hydrogen, Development, & Facts

    Oct 15, 2025 · The Bohr model is a description of the structure of atoms proposed in 1913 by the Danish physicist Niels Bohr. The Bohr model of the atom, a radical departure from earlier, …

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

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