Atoms and Elements Study Notes

Chapter 4 - Atoms and Elements

1. Evolution of the Modern View of an Atom

  • Introduction to Atoms: Describes early concepts of atomic theory and images (e.g., STM image of Nickel Atoms by IBM Corporation).

2. Historical Foundations of Atomic Theory

2.1 Key Contributors to Atomic Theory

  • Antoine Lavoisier (1774):

    • Introduced the Law of Conservation of Mass: In a chemical reaction, matter is neither created nor destroyed, hence the total mass of reactants equals total mass of products.

  • Joseph Proust (1799):

    • Formulated the Law of Constant Composition (also known as the Law of Definite Proportions): All samples of a given compound, regardless of source or preparation method, have the same proportions of constituent elements.

  • John Dalton (1803-1888):

    • Developed Atomic Theory and introduced the Law of Multiple Proportions: When two elements form more than one compound, the masses of one element combined with a fixed mass of the other are in small whole number ratios.

3. Dalton’s Atomic Theory

3.1 Major Postulates of Dalton’s Theory
  1. Each element is composed of atoms.
  2. All atoms of a given element are identical in mass and properties.
  3. Compounds are combinations of different atoms.
  4. A chemical reaction involves the rearrangement of atoms; no atoms are created or destroyed.
3.2 Consequences of Dalton’s Theory
  • Example of Law of Multiple Proportions:
    • In forming carbon monoxide: 1.0 g of carbon combines with 1.33 g of oxygen.
    • In forming carbon dioxide: 1.0 g of carbon combines with 2.66 g of oxygen.

4. Discoveries of Subatomic Particles

4.1 Key Experiments and Discoveries
  • J. J. Thomson:
    • Conducted cathode ray tube experiments, leading to the discovery of the electron.
    • Proposed the Plum-Pudding Model of the atom, consisting of negatively charged electrons surrounded by a positively charged