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  2. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules or crystals. The ability of atoms to attach and detach from each other is responsible for most of the physical changes observed in nature. Chemistry is the science that studies these changes.

  3. Ball-and-stick model - Wikipedia

    en.wikipedia.org/wiki/Ball-and-stick_model

    In chemistry, the ball-and-stick model is a molecular model of a chemical substance which displays both the three-dimensional position of the atoms and the bonds between them. [1] The atoms are typically represented by spheres , connected by rods which represent the bonds.

  4. Structural formula - Wikipedia

    en.wikipedia.org/wiki/Structural_formula

    Skeletal structural formula of Vitamin B 12.Many organic molecules are too complicated to be specified by a molecular formula.. The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space.

  5. Lewis structure - Wikipedia

    en.wikipedia.org/wiki/Lewis_structure

    A simpler method has been proposed for constructing Lewis structures, eliminating the need for electron counting: the atoms are drawn showing the valence electrons; bonds are then formed by pairing up valence electrons of the atoms involved in the bond-making process, and anions and cations are formed by adding or removing electrons to/from the ...

  6. Nuclear fission product - Wikipedia

    en.wikipedia.org/wiki/Nuclear_fission_product

    The sum of the atomic mass of the two atoms produced by the fission of one fissile atom is always less than the atomic mass of the original atom. This is because some of the mass is lost as free neutrons, and once kinetic energy of the fission products has been removed (i.e., the products have been cooled to extract the heat provided by the reaction), then the mass associated with this energy ...

  7. Chemical element - Wikipedia

    en.wikipedia.org/wiki/Chemical_element

    Atoms of one element can be transformed into atoms of a different element in nuclear reactions, which change an atom's atomic number. Historically, the term "chemical element" meant a substance that cannot be broken down into constituent substances by chemical reactions, and for most practical purposes this definition still has validity.

  8. Electron shell - Wikipedia

    en.wikipedia.org/wiki/Electron_shell

    In chemistry and atomic physics, an electron shell may be thought of as an orbit that electrons follow around an atom's nucleus.The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on further and further from the nucleus.

  9. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    The periodic table and law are now a central and indispensable part of modern chemistry. The periodic table continues to evolve with the progress of science. In nature, only elements up to atomic number 94 exist; [a] to go further, it was necessary to synthesize new elements in the laboratory.