CHEMISTRY LAB REPORT

Chemistry lab report

Chemistry lab report

The behavior of electrons in molecules and atoms is described by quantum mechanics; classical (Newtonian) mechanics cannot be used because the de Broglie wavelengths (?=h/mv) of the electrons are comparable with molecular (and atomic) dimensions. The relevant quantum-mechanical ideas are as follows:

Electrons are characterized by their entire distributions (called wave functions or orbitals) rather than by instantaneous positions and velocities: an electron may be considered always to be (with appropriate probability) at all points of its distribution (which does not vary with time)(Atkins, 20090. Other things being equal, the kinetic energy of an electron decreases as the volume occupied by the bulk of its distribution increases, so delocalization lowers its kinetic energy.

KE=p22m=h22m? 2˜A D2˜A V 2 3

The potential energy of interaction between an electron and other charges is as calculated by classical physics, using the appropriate distribution (wave function) for the electron: an electron distribution is therefore attracted by nuclei and its potential energy decreases as the average electron-nuclear distance decreases.

PE ˜ -B/D ˜ -B/V1/3

A minimum-energy electron distribution represents the best compromise between concentration near the nuclei (to reduce potential energy) and delocalization (to reduce kinetic energy).

E=KE+PE˜ A/V 2/3-B/V1/3

A bond will form between two atoms when the electron distribution of the combined atoms (molecular orbital) yields a significantly lower energy than the separate-atom distributions (atomic orbitals). An example is a covalent bond, in which two electrons, one originally on each atom, change their distributions so that each extends over both atoms.

Molecules are little things not susceptible of direct fact even under the most mighty microscope. However, their properties can be deduced obscurely from experiments. These things are distinct on the conceptual grade as well.

Classical physics can no longer offer a reliable description. It is restored by quantum idea, which recounts the ...