5 Matching Annotations
  1. Oct 2018
    1. In contrast to his concept of a simple circular orbit with a fixed radius, orbitals are mathematically derived regions of space with different probabilities of having an electron.

      In this case, the QM model allows for probabilistic radii, not fixed radii, and the quantization is the energy level. An electron with principal quantum number n = 2 will always have quantized energy corresponding to \( E = R(1/n^2) \), but the exact minimal and maximal radial distance from the nucleus is not specified as in the Bohr model of the atom. Similar to the Bohr model though, the most probable radial distance is quantifiable, and that is the radius the electron is most likely to inhabit, however it will be found elsewhere at other times.

    1. Because all the 2p orbitals are degenerate

      Degeneracy has not yet been defined.

      Degeneracy was defined under the heading Orbital Energies in section 1.6, Representation of Orbitals.

    1. Notice in Figure 2.1.1 that the difference in energies between subshells can be so large that the energies of orbitals from different principal shells can become approximately equal. For example, the energy of the 3d orbitals in most atoms is actually between the energies of the 4s and the 4p orbitals.

      The energy of a shell (not a sub-shell) is calculated with R(1/n^2), with n being the energy level of interest. However, due to penetration and shielding, the outer electrons do not experience the full attraction of the nucleus, and we see this in the sub-shells of different principal quantum numbers being staggered, rather than linear. There should be equations to calculate the energy of a specific sub-shell, but I am not aware of them and I cannot find them in the text.

  2. Sep 2018
    1. correct number of significant figures

      This is a fact of measurement; think of the meniscus in a volumetric flask, we know that we have exactly 50.Xml; when filled to the 50ml mark, the meniscus is the volume of water which through fluidic tension is changed in shape from a perfect flat surface to a conic shape; we take measurement at the bottom of the meniscus to preserve accuracy in our measurement, so the last figure in our measurement is an estimate.

      In a measure of 50.1ml of fluid, the 100 microlitres is an estimate of the volume of fluid in the meniscus.