Physical Chemistry

Concept Of Hybridization

     While formation of simple molecules could be explained adequately by overlap of atomic orbitals, the formation of molecules of Be, B and C present problems of greater magnitude having no solution with the previous theory. To explain fully the tendency of these atoms to form bonds and the …

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Bond Formation, (σ) Bond and (π) Bond

Bond Formation (Valence Bond Theory) – Bond formation between atoms to give chemical compounds can be interpreted admirably in terms of the orbital theory of atomic structure. – Heitler and London believed that electron cloud of the valence orbital on one atom ‘overlaps’ the electron cloud of the other bonding …

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Bond Dissociation Energy

  Bond Dissociation Energy   ** Bond breaking can be quantified using the bond dissociation energy. **The bond dissociation energy is the energy needed to homolytically cleave a covalent bond.   ** The energy absorbed or released in any reaction, symbolized by ΔH°, is called the enthalpy change or heat …

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Metallic Bonding

  Metallic Bonding   ** The valence bonds that hold the atoms in a metal crystal together are not ionic, nor are they simply covalent in nature. Ionic bonding is obviously impossible here since all the atoms would tend to give electrons but none are willing to accept them. Ordinary …

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Polar Covalent Bonds

Polar Covalent Bonds   ** In the H2or Cl2 molecule, the two electrons constituting the covalent bond are equally shared by the two identical nuclei. Due to even distribution of (+) and (–) charge, the two bonded atoms remain electrically neutral. Such a bond is called nonpolar covalent bond. ** …

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Hydrogen Bonding (H-Bonding)

  Hydrogen Bonding – (H-Bonding)   ** When hydrogen (H) is covalently bonded to a highly electronegative atom X (O, N, F), the shared electron pair is pulled so close to X that a strong dipole results   ** Since the shared pair is removed farthest from H atom, its …

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Co-ordinate Covalent bond

Co-ordinate Covalent bond   ** In a normal covalent bond, each of the two bonded atoms contributes one electron to make the shared pair. ** In some cases, a covalent bond is formed when both the electrons are supplied entirely by one atom. Such a bond is called co-ordinate covalent …

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Covalent Bond

Covalent Bond   ** The electron transfer theory could not explain the bonding in molecules such as H2, O2, Cl2 etc., and in organic molecules, that had no ions. ** It was G.N. Lewis who suggested that two atoms could achieve stable 2 or 8 electrons in the outer shell by …

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Ionic Bond

  Ionic Bond   ** This type of bond is established by transfer of an electron from one atom to another. ** Let us consider a general case when an atom A has one electron in the valence shell and another atom B has seven electrons. A has one electron …

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Nuclear Fusion Process

  Nuclear Fusion Process   ** This process is opposite of nuclear fission. ** Nuclear fusion may be defined as : the process in which two light-weight nuclei combine or fuse to form a single heavier nucleus. ** The following  figure shows Illustration of fusion of two deuterium (2H1) nuclei to form …

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Nuclear Reactor

  Nuclear Reactor ** It has been possible to control fission of U-235 so that energy is released slowly at a usable rate. ** Controlled fission is carried out in a specially designed plant called a nuclear power reactor or simply nuclear reactor.  ** The chief components of a nuclear reactor are: (1) U-235 …

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Nuclear Fission Process

  Nuclear Fission Process   ** In 1939, Hahn and Stassmann discovered that a heavy atomic nucleus as of uranium-235 upon bombardment by a neutron splits apart into two or more nuclei. U-235 first absorbs a neutron to form an unstable ‘compound nucleus’. The excited ‘compound nucleus’ then divides into …

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