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  2. Aufbau principle - Wikipedia

    en.wikipedia.org/wiki/Aufbau_principle

    In atomic physics and quantum chemistry, the Aufbau principle (/ ˈ aʊ f b aʊ /, from German: Aufbauprinzip, lit. 'building-up principle'), also called the Aufbau rule, states that in the ground state of an atom or ion, electrons first fill subshells of the lowest available energy, then fill subshells of higher energy. For example, the 1s ...

  3. 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.

  4. Molecular model - Wikipedia

    en.wikipedia.org/wiki/Molecular_model

    Note the snipped stubs representing hydrogen atoms. A good example of composite models is the Nicholson approach, widely used from the late 1970s for building models of biological macromolecules. The components are primarily amino acids and nucleic acids with preformed residues representing groups of atoms. Many of these atoms are directly ...

  5. 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.

  6. Atomic orbital - Wikipedia

    en.wikipedia.org/wiki/Atomic_orbital

    They can be obtained analytically, meaning that the resulting orbitals are products of a polynomial series, and exponential and trigonometric functions. (see hydrogen atom). For atoms with two or more electrons, the governing equations can be solved only with the use of methods of iterative approximation.

  7. Ionic bonding - Wikipedia

    en.wikipedia.org/wiki/Ionic_bonding

    Strongly electronegative atoms (such as halogens) often have only one or two empty electron states in their valence shell, and frequently bond with other atoms or gain electrons to form anions. Weakly electronegative atoms (such as alkali metals ) have relatively few valence electrons , which can easily be lost to strongly electronegative atoms.

  8. Molecular mechanics - Wikipedia

    en.wikipedia.org/wiki/Molecular_mechanics

    A force field is used to minimize the bond stretching energy of this ethane molecule.. Molecular mechanics uses classical mechanics to model molecular systems. The Born–Oppenheimer approximation is assumed valid and the potential energy of all systems is calculated as a function of the nuclear coordinates using force fields.

  9. 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 ...