Carbocations

Carbocations are species bearing a formal "+" charge on carbon. The have sp² hybridization and trigonal planar geometry, with an empty p orbital on carbon, perpendicular to the plane containing the substituents (see diagrams shown to the right). Carbocations are "hypovalent" species, inasmuch as they have only three shared pairs of electrons around carbon, instead of the usual four. Of course, this incomplete octet around carbon makes carbocations very unstable and very reactive. Nevertheless, carbocations are known to be formed as intermediates in many types of organic reactions. For more details click here.

Courtesy: Dr. Thomas H. Eberlein, Penn State University

Langmuir Isotherm

The chemistry of adsorption is relatively complicated. A host of theories have been used in an attempt to understand the adsorption process. On this article, we will briefly introduce you to some of the math used to model adsorption, but you should be aware that this is only one model. 

We will assume an understanding of basic algebra throughout the discussion. You will need to know how to graph data and how to find the slope and y-intercept of a line. For more details click here.

Derivation of the Langmuir isotherm is here

Courtesy: http://water.me.vccs.edu

Racemic mixture

In chemistry, a racemic mixture, or racemate (pronounced /reɪˈsimeɪt/), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule. The first known racemic mixture was "racemic acid", which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. For more details click here.

 

Courtesy: http://www.princeton.edu

Valence Shell Electron Pair Repulsion Theory

VSEPR theory proposes that the geometric arrangement of terminal atoms, or groups of atoms about a central atom in a covalent compound, or charged ion, is determined solely by the repulsions between electron pairs present in the valence shell of the central atom. For more details click here.

Courtesy: http://intro.chem.okstate.edu

Valence Bond Theory and Hybrid Atomic Orbitals

The valence-bond approach considers the overlap of the atomic orbitals (AO) of the participation atoms to form a chemical bond. Due to the overlapping, electrons are localized in the bond region. The overlapping AOs can be of different types, for example, a sigma bond may be formed by the overlapping the following AOs.  For more details click here.

 Courtesy: http://www.science.uwaterloo.ca

Blog Special Edition

Calculations reveal carbon-carbon quadruple bond

 Courtesy: Andy Extance, http://www.rsc.org

Nanotechnology Basics: For Students and Other Learners

"The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big." — 

Richard Feynman, Nobel Prize winner in physics 

For more details click here

 

Courtesy: http://www.crnano.org

Basic Molecular Dynamics

A working definition of molecular dynamics (MD) simulation is technique by which one generates the atomic trajectories of a system of N particles by numerical integration of Newton’s equation of motion, for a specific inter-atomic potential, with certain initial condition (IC) and boundary condition (BC).

Consider, for example (see Figure), a system with N atoms in a volume . We can define its internal energy: E ≡ K +U, where K is the kinetic energy. For more details click here.

 Courtesy: Ju Li, Ohio State University, Columbus, OH, USA

Infrared Spectroscopy

The light our eyes see is but a small part of a broad spectrum of electromagnetic radiation. On the immediate high energy side of the visible spectrum lies the ultraviolet, and on the low energy side is the infrared. The portion of the infrared region most useful for analysis of organic compounds is not immediately adjacent to the visible spectrum, but is that having a wavelength range from 2,500 to 16,000 nm, with a corresponding frequency range from 1.9*10¹³ to 1.2*10¹⁴ Hz. For more details click here.

Courtesy: Dr. Reusch, http://www2.chemistry.msu.edu

Nuclear Chemistry

Nuclear chemistry is the sub-discipline of chemistry that is concerned with changes in the nucleus of elements. These changes are the source of radioactivity and nuclear power. Since radioactivity is associated with nuclear power generation, the concomitant disposal of radioactive waste, and some medical procedures, everyone should have a fundamental understanding of radioactivity and nuclear transformations in order to evaluate and discuss these issues intelligently and objectively. For more details click here. 

courtesy: http://nnhschemistry.pbworks.com

Courtesy: http://www.sas.upenn.edu

Analytical Chemistry

Analytical chemistry began in the late eighteenth century with the work of French chemist Antoine-Laurent Lavoisier and others; the discipline was further developed in the nineteenth century by Carl Fresenius and Karl Friedrich Mohr. As a pharmacist's apprentice in Frankfurt, Germany, Fresenius developed an extensive qualitative analysis scheme that, when it was later published, served as the first textbook of analytical chemistry. He built a laboratory at his house that opened in 1848. Here he trained students in gravimetric techniques that he had developed. Mohr developed laboratory devices such as the pinch clamp burette and the volumetric pipette. He also devised a colorimetric endpoint for silver titrations. It was his 1855 book on titrimetry, Lehrbuch der Chemisch-Analytischen Titromethode , that generated widespread interest in the technique.

Read more: http://www.chemistryexplained.com/A-Ar/Analytical-Chemistry.html#ixzz2E0G5tLhf

What is science?

The word "science" probably brings to mind many different pictures: a fat textbook, white lab coats and microscopes, an astronomer peering through a telescope, a naturalist in the rainforest, Einstein's equations scribbled on a chalkboard, the launch of the space shuttle, bubbling beakers …. All of those images reflect some aspect of science, but none of them provides a full picture because science has so many facets: more details can be found here.

These images all show an aspect of science, but a complete view of science is more than any particular instance.

 Courtesy: http://undsci.berkeley.edu