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  ❒ 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, …

  Atomic Spectra ❒When an element in the vapour or the gaseous state is heated in a flame or a discharge tube, the atoms are excited (energised) and emit light radiations of a characteristic colour. The colour of light produced indicates the wavelength of the radiation emitted.       …

  Mosley’s Determination of Atomic number ❒ The discovery that atom has a nucleus that carries a positive charge raised the question : What is the magnitude of the positive charge? This question was answered by Henry Mosley in 1913. ❒ Hitherto atomic number was designated as the ‘position number’ …

  Alpha particles ❒ Alpha particles are shot out from radioactive elements with very high speed. ❒ For example, they come from radium atoms at a speed of 1.5 × 107m/sec. Rutherford identified them to be di-positive helium ions, He2+or 4He2. Thus an alpha particle has 2+ charge and 4 …

Subatomic Particles ❒We have hitherto studied the properties of the three principal fundamental particles of the atom, namely the electron, proton, and neutron. These are summarised in this Table:   ❒Nearly all of the ordinary chemical properties of matter can be examined in terms of atoms consisting of electrons, protons …

Cathode Rays – The discovery of electron ❒The knowledge about the electron was derived as a result of the study of the electric discharge in the discharge tube (J.J. Thomson, 1896).   (1) The discharge tube consists of a glass tube with metal electrodes fused in the walls. (2) Through …

Substituted Cyclohexanes: Axial and Equatorial Hydrogen Groups ❒The six-membered ring is the most common ring found among nature’s organic molecules. For this reason, we shall give it special attention. We have already seen that the chair conformation of cyclohexane is the most stable one and that it is the predominant …

  Conformations of Cyclohexane: The Chair and the Boat ❒ Cyclohexane is more stable than the other cycloalkanes we have discussed, and it has several conformations that are important for us to consider. (1) The most stable conformation of cyclohexane is the chair conformation. (2) There is no angle or torsional …

    ❒ Carboxylic acids are weak acids, typically having pKa values in the range of 3–5. Alcohols, by comparison, have pKa values in the range of 15–18, and essentially do not give up a proton unless exposed to a very strong base. ❒ To understand the reasons for this difference, let’s consider acetic acid …