Physical Chemistry

  preface of This book      The book is divided into four parts. The first part focuses on the macroscopic properties of physical systems. It begins with the descriptive study of gases and liquids, and proceeds to the study of thermodynamics, which is a comprehensive macroscopic theory of the behavior …

  preface of This book      Two very important fields of natural science—chemistry and the science of electricity— matured and grew vigorously during the first half of the nineteenth century. Electrochemistry developed simultaneously. From the very beginning, electrochemistry was not merely a peripheral field but evolved with an important …

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 …

    1. The valency of an element is ___________ (a) the combining capacity of one atom of it (b) the number of bonds formed by its one atom (c) the number of hydrogen atoms that combine with one atom of it (d) all the above Answer. (d) 2. The …

  VSEPR Theory   ** The Lewis structure of a molecule tells us the number of pairs of electrons in the valence shell of the central atom. These electron pairs are subject to electrostatic attractions between them. On this basis, R.G.Gillespie (1970) proposed a theory called the Valence-Shell Electron Pair …

  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 …

  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 …

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. ** …

  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 …

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 …

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 …

  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 …

  Chemical Bond   ** Molecules of chemical substances are made of two or more atoms joined together by some force, acting between them. This force which results from the interaction between the various atoms that go to form a stable molecule, is referred to as a Chemical Bond. ** A …

    1. Which is the correct symbol for an alpha particle? (a) 4He2 (b) 1n0 (c) 0e-1 (d) 1p1 Answer. (a) 2. Of the following, which is the most damaging when ingested? (a) beta emitters (b) alpha emitters (c) gamma emitters (d) all of these Answer. (b) 3. An …

  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 …