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  2. Nuclear fission - Wikipedia

    en.wikipedia.org/wiki/Nuclear_fission

    Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay. Nuclear fission was discovered by chemists Otto Hahn and Fritz Strassmann and physicists Lise ...

  3. Discovery of nuclear fission - Wikipedia

    en.wikipedia.org/wiki/Discovery_of_nuclear_fission

    The nuclear reaction theorised by Meitner and Frisch and observed by Hahn and Strassmann. Nuclear fission was discovered in December 1938 by chemists Otto Hahn and Fritz Strassmann and physicists Lise Meitner and Otto Robert Frisch. Fission is a nuclear reaction or radioactive decay process in which the nucleus of an atom splits into two or ...

  4. Lewis structure - Wikipedia

    en.wikipedia.org/wiki/Lewis_structure

    When Be is bonded with 2 other atoms, or when B and Al are bonded with 3 other atoms, they do not form full valence shells. Assume single bonds and use the actual bond number to calculate lone pairs. Expanded Octet (only occurs for elements in Groups 3-8) Bond calculation will provide too few bonds for the number of atoms in the molecule.

  5. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    It is determined by the number of bonds it can form to other atoms or groups. [92] The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in that shell are called valence electrons. The number of valence electrons determines the bonding behavior with other atoms.

  6. Octet rule - Wikipedia

    en.wikipedia.org/wiki/Octet_rule

    Octet rule. The bonding in carbon dioxide (CO 2): all atoms are surrounded by 8 electrons, fulfilling the octet rule. The octet rule is a chemical rule of thumb that reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a ...

  7. History of molecular theory - Wikipedia

    en.wikipedia.org/wiki/History_of_molecular_theory

    An electron may form a part of the shell of two different atoms and cannot be said to belong to either one exclusively. Moreover, he proposed that an atom tended to form an ion by gaining or losing the number of electrons needed to complete a cube. Thus, Lewis structures show each atom in the structure of the molecule using its chemical symbol.

  8. Nuclear binding energy - Wikipedia

    en.wikipedia.org/wiki/Nuclear_binding_energy

    For example, the dalton (1 Da) is defined as 1/12 of the mass of a 12 C atom—but the atomic mass of a 1 H atom (which is a proton plus electron) is 1.007825 Da, so each nucleon in 12 C has lost, on average, about 0.8% of its mass in the form of binding energy.

  9. Chemical bond - Wikipedia

    en.wikipedia.org/wiki/Chemical_bond

    A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bonds, or some combination of these effects.