Valence shell electron pair repulsion theory (VSEPR) as explained in most textbooks predicts that substituents bonded to a central atom in AX[subscript n]E[subscript z][superscript c] species (A = main-group central atom, X = substituent, E = lone pair on central atom, c = charge) will change their X-A-X angles to bend away from the lone pairs.…

In this article, we describe a fully computational laboratory exercise that results in an increase of students' understanding of what quantum chemical geometry optimization calculations are doing to find minimum energy structures. This laboratory exercise was conducted several times over multiple years at a small private undergraduate institution,…

One of the main topics of elementary physics is the idea that every material is composed of "little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one other." These particles could be atoms or molecules. Atoms are the smallest part into…

The concept of an atom with an expanded octet, known as hypervalency, has persisted in the general chemistry curriculum, despite abundant theoretical work disputing its veracity. Here, the electronic structure of traditionally hypervalent molecules (H[subscript 2]SO[subscript 3], H[subscript 2]SO[subscript 4], PF[subscript 5], and SF[subscript 6])…

In this work, two exercises are described that are designed to teach students about the evolution and behavior of the electronic bands of graphene and bilayer graphene. These exercises involve performing extended Hückel molecular orbital theory calculations on polyacenes and polycyclic aromatic hydrocarbons. In the first exercise, students…

Students often wrestle unsuccessfully with the task of correctly calculating momentum probability densities and have difficulty in understanding their interpretation. In the case of a particle in an "infinite" potential well, its momentum can take values that are not just those corresponding to the particle's quantised energies but…

Franck-Condon factors (FCFs) play a crucial role in determining the intensities of the vibrational bands in electronic transitions. In this article, a relatively simple method to calculate the FCFs is illustrated. An algorithm for the Fourier Grid Hamiltonian (FGH) method for computing the vibrational wave functions and the corresponding energy…

The advantages of Gaussian-type orbitals (GTO) over Slater-type orbitals (STO) in quantum chemistry calculations are clarified here by means of a holistic approach. The popular Microsoft Office Excel program was used to create an interactive application with which students are able to explore the features of GTO, including automatic calculations…

The history of Laplace's equations for spherical and cylindrical droplets and the concept of dividing surface in Gibbs' thermodynamic theory of capillary phenomena are briefly reviewed. The existing theories of surface tensions of cylindrical droplets are briefly reviewed too. For cylindrical droplets, a new method to calculate the radius and the…

Our understanding of carbonium ions as intermediates in chemical reaction mechanisms derives from the early work of Julius Stieglitz and the more famous Hans Meerwein, the latter studying the racemization of isobornyl chloride when treated with Lewis acids. This review analyzes how key mechanistic concepts for this reaction evolved and gives the…

Relatively few undergraduate physical chemistry programs integrate molecular modeling into their quantum mechanics curriculum owing to concerns about limited access to computational facilities, the cost of software, and concerns about increasing the course material. However, modeling exercises can be integrated into an undergraduate course at a…

The Morse-Pekeris oscillator model for the calculation of the vibration-rotation energy levels of diatomic molecules is revisited. This model is based on the realization of a second-order exponential expansion of the centrifugal term about the minimum of the vibrational Morse oscillator and the subsequent analytical resolution of the resulting…

Using an easy-to-make cylindrical resonator, students can measure the speed of sound in a gas, u, with sufficiently high precision (by locating standing-wave Lissajous patterns on an oscilloscope) to observe real gas properties at one atmosphere and 300 K. For CO[subscript 2] and SF[subscript 6], u is found to be 268.83 and 135.25 m s[superscript…

For 137 years Markovnikov's rule has been extensively used in organic chemical education and research to describe the regioselectivity in electrophilic addition reactions to alkenes and alkynes. When the structures of the final reaction products are used as reference, the rule requests that certain polar addition reactions be termed…