From Chemistry For Dummies, 2nd Edition by John T. Moore
During the first year of high school chemistry or the first semester of college chemistry, all the terms, units of measurement, and atoms, molecules, elements, and compounds may seem a bit overwhelming. The good news: Your Chem I class doesn't have to be torture. This handy Cheat Sheet provides some basic information you can refer to regularly to make your chemistry class just a tiny bit easier. Chemical Bonding Basics
In bonding, atoms lose, gain, or share electrons in order to have the same number of electrons as the noble gas that's nearest on the periodic table. Ionic, covalent, and metallic bonds are formed by combinations of metals and nonmetals. * Metal + nonmetal = ionic bond
* Nonmetal + nonmetal = covalent bond
* Metal + metal = metallic bond
When two elements engage in ionic bonding, one or more electrons are transferred from the metal to the nonmetal, forming ions (charged atoms). The metal, having lost one or more electrons, forms a cation, an ion with a positive charge; the nonmetal, having gained one or more electrons, becomes an anion, an ion with a negative charge. When two elements form a covalent bond, one or more electron pairs are shared between these two elements. In metallic bonding, which occurs in metals (either a pure metal or an alloy of two or more metals), the valence (outer shell) electrons are donated to a "sea of electrons." Chemistry Concepts: Energy Levels and Orbitals
A lot of chemistry is explained by the sharing and trading of electrons between atoms. Understanding how electrons are arranged in an atom is a building block of Chem I. Electrons in an atom are contained in specific energy levels (1, 2, 3, and so on) that are different distances from the nucleus. The larger the number of the energy level, the farther it is from the nucleus. Electrons that are in the highest energy level are called valence electrons. Within each energy...