General Chemistry

Reactivity of the Substrate in SN2 Reactions – We will often refer to the alkyl halide as the substrate: literally, the compound that is being attacked by the reagent. – Just as the nucleophile is important in the SN2 reaction, the structure of the alkyl halide is equally important. – …

  ❒ In the previous subject we talk about but electronic structures and bonding properties of some of The homonuclear diatomic molecules. but in this subject we will talk about Molecular Orbitals for Heteronuclear Diatomic Molecules (MO Theory) ❒ When two different atoms are bonded together, their molecule is called heteronuclear molecule. ❒ …

    After having discussed the basic principles of Molecular Orbital Theory, we are now able to take up the electronic structures and bonding properties of some of the homonuclear diatomic molecules. (1) Hydrogen, H2 ❒ Hydrogen molecule is formed from 1s1 atomic orbitals of two atoms. They give rise …

    1. When a chemical bond between two atoms is formed, the potential energy of the system_______ (a) decreases (b) increases (c) remains the same (d) cannot be predicted Answer. (a) 2. According to valence bond theory, a bond between two atoms is formed when_______ (a) half filled atomic …

  Molecular Orbital Theory ❒ Molecular orbital theory proposed by Hund and Mulliken in 1932 explains the formation of a covalent bond in a better way.  ❒ According to molecular orbital theory all atomic orbitals of the atoms participating in molecule formation get disturbed when the concerned nuclei approach nearer. …

    1. According to de Broglie’s equation, the momentum of a particle in motion is _______ proportional to wavelength. (a) inversely (b) directly (c) is not (d) none of these Answer. (a) 2. The wavelength of large objects is of no significance as it is too _______ to be …

  Electron Affinity  ❒ A neutral atom can accept an electron to form negative ion. In this process, in general, energy is released.  ❒ Electron affinity (EA) of an element: is the amount of energy released when an electron is added to a gaseous atom to form an anion.   …

  Ionization Energy ❒ The process of removing an electron from an isolated atom to form a positive ion is called ionisation. Energy will be required to remove an electron from the atom against the force of attraction of the nucleus. ❒ The ionisation energy (IE) of an element: is …

  Electron Configuration Of Elements ❒ We have seen before that to define completely the state of an atom it is obligatory to refer to all the four quantum numbers (n, l, m and s) of every electron in it. ❒ Since a simultaneous representation of all quantum numbers of …

Energy Distribution and Orbitals ❒ In our earlier discussion we have seen that the energy of an electron is determined by the first two quantum numbers (n) and (l), while the other two specify the orientation of the electron orbital in space and the spin. ❒ As we discuss the …

  Pauli’s Exclusion Principle ❒  The nature of an electron, its position and energy, is fully implied only by mentioning the values of four quantum numbers ascribed to it. ❒ Each electron is, therefore, fully characterised by a set of four quantum numbers (n) – giving the size of electron …

  Quantum Numbers ❒ Bohr’s electronic energy shells or levels, designated as Principal Quantum Numbers (n), could hardly explain the hydrogen spectrum adequately. Spectra of other elements that are quite complex, also remained unexplained by this concept. ❒ Many single lines of the spectra are found to consist of a …

  Schrödinger’s Wave Equation ❒ In order to provide sense and meaning to the probability approach, Schrödinger derived an equation known after his name as Schrödinger’s Wave Equation.  ❒ Calculation of the probability of finding the electron at various points in an atom was the main problem before Schrödinger.    ❒ His …

  Heisenberg’s uncertainty Principle ❒One of the most important consequences of the dual nature of matter is the uncertainty principle developed by Werner Heisenberg in 1927. ❒ This principle is an important feature of wave mechanics and discusses the relationship between a pair of conjugate properties (those properties that are …

    1. Cathode rays are deflected by_______ (a) electric field only (b) magnetic field only (c) electric and magnetic field (d) none of these Answer. (c) 2. The e/m value for the particles constituting cathode rays is the same regardless of_______ (a) the gas present in cathode rays tube …

  De Broglie’s Equation ❒de Broglie had arrived at his hypothesis with the help of Planck’s Quantum Theory and Einstein’s Theory of Relativity. ❒He derived a relationship between the magnitude of the wavelength associated with the mass (m) of a moving body and its velocity. ❒According to Planck, the photon …

  Zeeman Effect ❒ In 1896 Zeeman discovered that spectral lines are split up into components when the source emitting lines is placed in a strong magnetic field. It is called the Zeeman effect after the name of the discoverer. ❒ The apparatus used to observe Zeeman effect is shown …

   Having known that planetary electrons numerically equal to the atomic number are revolving about the atomic nucleus in closed orbits, the question arises as to how they are arranged in these orbits. Langmuir Scheme ❒ We are indebted to Langmuir for putting forward the first elaborate scheme of the …

  ❒ Rutherford’s nuclear model simply stated that atom had a nucleus and the negative electrons were present outside the nucleus. It did not say anything as to how and where those electrons were arranged. It also could not explain why electrons did not fall into the nucleus due to …

  Photoelectric Effect ❒When a beam of light of sufficiently high frequency is allowed to strike a metal surface in vacuum, electrons are ejected from the metal surface. This phenomenon is known as Photoelectric effect and the ejected electrons Photoelectrons.  ❒For example, when ultraviolet light shines on Cs (or Li, …