20Jun 2019 by Vincent Summers 1 Comment

A Simple Valence Problem for a Beginning Chemistry Enthusiast

Chemistry, Education
It is not unusual for school systems to introduce students to chemistry by means of the Periodic Table of the Elements. The table is then broken down into sections: the metals, the non-metals, and the gases. Before long, the structure of the atom is discussed, including protons, neutrons, electrons, orbitals, shells, and valence. It is the last of these we will briefly discuss here – valence. First a very brief discussion, followed by examples, followed by a puzzling problem (to impart insight). Valence: A Simple Discussion Atoms, although containing positive protons and negative electrons, have a net charge of zero. They are electrically neutral. This means each lone atom has a number of electrons equal to its number of protons. For instance, a sodium atom¹ has 11 protons. It also…
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10May 2019 by Vincent Summers No Comments

Electronegativity of Atoms: What are Determining Factors

Chemistry, Physics
[caption id="attachment_24637" align="alignright" width="480"] 5d molecular orbital - Image Dhatfield[/caption] When two different types of atom are bonded together, they do not share their bond electrons equally. This is because each type of atom possesses its own charge environment, which results in an atom’s electronegativity. Electronegativity is the measure of an atom’s ability to attract additional electron density to itself. For example, Sodium seeks to give an electron to become a positive ion, Na+. It has a very low electronegativity. Iodine wants to gain an electron to become a negative ion, I-. It has a relatively high electronegativity. Charge Environment Atoms vary in electronegativity, and bonds vary according to constituent atom electronegativities. The electronegativity of an atom depends upon its charge environment. That environment depends primarily on three things... Distance…
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15Apr 2019 by Vincent Summers 19 Comments

Rare Earth Metals – 17 Special Elements

Chemistry, Technology
[caption id="attachment_23646" align="alignright" width="480"] Rare Earths. Photo ARS-USDA by Peggy Grubb.[/caption] Most of us are familiar with elements – the building blocks of matter. Most of us know about elements such as oxygen, nitrogen, carbon, sulfur, sodium, and helium. Yet, there are other elements few have even heard of, despite their immense technological and medical importance. Are you familiar with the rare earth metals? Allow me to introduce them: what are they good for, and where do they come from? Rare Earth Metals Among the less commonly known elements are the rare earth metals. These elements have many important uses, such as: Rare earth metals are used in heat-resistant, powerful, permanent magnets. They are employed in superconductors for cryogenics applications. They are used in pyrophoric alloys for initiating combustion. And…
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27Nov 2014 by Vincent Summers No Comments

LCAO MO Chemical Bonding Theory and Examples

Chemistry
[caption id="attachment_8903" align="alignright" width="440"] Antibonding sigma orbital.[/caption] LCAO MO The nature of the chemical bond has been of interest for hundreds of years. Theories have been developed to explain how atoms combine to form molecules. The most successful theory to date is the (L)inear (C)ombination of (A)tomic (O)rbitals - (M)olecular (O)rbitals or LCAO MO bonding theory. You've got it: yet another acronym. Atoms have nuclei. These contain protons and neutrons. Electrons travel around these nuclei. Orbitals are mathematical functions that describe their trajectories. As atoms form molecules, atomic orbitals combine to form molecular orbitals. Since orbital functions are described by the Schrödinger wave equation and that equation is linear, molecular orbitals can be described by the linear additive combining of atomic orbitals. Example of Hydrogen Ordinary hydrogen has one proton,…
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10Nov 2014 by Vincent Summers No Comments

What Are Hybrid Atomic Orbitals?

Chemistry
[caption id="attachment_6346" align="alignright" width="440"] Pre-hybridization 1s, 2s, 2px, 2py, and 2pz atomic orbitals.[/caption] An atom consists of two components - a nucleus and its orbiting electrons. Nuclei contain neutrons and protons bound together by nuclear force. Electrons travel in well-defined atomic orbitals outside the nucleus. Orbitals come in different shapes. They contain up to two electrons each. A collection of orbits forms an electron shell. Atoms can have more than one shell. Orbitals and shells are identified by letters and numbers. The details are beyond the scope of this article; however, atoms begin filling electron orbitals in the order, Orbitals: s, p, d, f... Shells: 1, 2, 3, 4... First Elements Thus the first ten elements fill their orbitals and shells, Hydrogen 1s¹ Helium 1s² Lithium 1s² 2s¹ Beryllium 1s²…
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