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  2. Hund's rule of maximum multiplicity - Wikipedia

    en.wikipedia.org/wiki/Hund's_Rule_of_Maximum...

    For example, the nitrogen atom ground state has three unpaired electrons of parallel spin, so that the total spin is 3/2 and the multiplicity is 4. The lower energy and increased stability of the atom arise because the high-spin state has unpaired electrons of parallel spin, which must reside in different spatial orbitals according to the Pauli ...

  3. Multiplicity (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Multiplicity_(chemistry)

    Each has two electrons of opposite spin in the π* level so that S = 0 and the multiplicity is 2S + 1 = 1 in consequence. In the first excited state, the two π* electrons are paired in the same orbital, so that there are no unpaired electrons. In the second excited state, however, the two π* electrons occupy different orbitals with opposite spin.

  4. Molecular orbital diagram - Wikipedia

    en.wikipedia.org/wiki/Molecular_orbital_diagram

    The σ from the 2p is more non-bonding due to mixing, and same with the 2s σ. This also causes a large jump in energy in the 2p σ* orbital. The bond order of diatomic nitrogen is three, and it is a diamagnetic molecule. [12] The bond order for dinitrogen (1σ g 2 1σ u 2 2σ g 2 2σ u 2 1π u 4 3σ g 2) is three because two electrons are now ...

  5. Valence bond theory - Wikipedia

    en.wikipedia.org/wiki/Valence_bond_theory

    Pi bonds occur when two orbitals overlap when they are parallel. [9] For example, a bond between two s-orbital electrons is a sigma bond, because two spheres are always coaxial. In terms of bond order, single bonds have one sigma bond, double bonds consist of one sigma bond and one pi bond, and triple bonds contain one sigma bond and two pi bonds.

  6. Three-center four-electron bond - Wikipedia

    en.wikipedia.org/.../Three-center_four-electron_bond

    Using this model, one sidesteps the need to invoke hypervalent bonding considerations at the central atom, since the bonding orbital effectively consists of two 2-center-1-electron bonds (which together do not violate the octet rule), and the other two electrons occupy the non-bonding orbital.

  7. Three-center two-electron bond - Wikipedia

    en.wikipedia.org/wiki/Three-center_two-electron_bond

    A B−H−B 3-center-2-electron bond is formed when a boron atom shares electrons with a B−H bond on another boron atom. The two electrons (corresponding to one bond) in a B−H−B bonding molecular orbital are spread out across three internuclear spaces. [1] In diborane (B 2 H 6), there are two such 3c-2e bonds: two H atoms bridge the two B ...

  8. Bond order - Wikipedia

    en.wikipedia.org/wiki/Bond_order

    In chemistry, bond order is a formal measure of the multiplicity of a covalent bond between two atoms. As introduced by Gerhard Herzberg, [1] building off of work by R. S. Mulliken and Friedrich Hund, bond order is defined as the difference between the numbers of electron pairs in bonding and antibonding molecular orbitals.

  9. Molecular orbital theory - Wikipedia

    en.wikipedia.org/wiki/Molecular_orbital_theory

    Bond order is the number of chemical bonds between a pair of atoms. The bond order of a molecule can be calculated by subtracting the number of electrons in anti-bonding orbitals from the number of bonding orbitals, and the resulting number is then divided by two. A molecule is expected to be stable if it has bond order larger than zero.