Truthfully, the transition metals do not behave with such simple rules as the other elements, so for the purposes of this discussion, we will pretend they do not exist (just close your eyes and pretend!). Additionally, I have completely neglected the transition metals (atoms with group numbers ranging from 3 to 12). Other types of bonds (such as hydrogen bonds) are too weak to influence the location of the electrons relative to their atoms, so we are safe in only considering covalent bonds. By convention, Lewis structures only apply to covalently bonded molecules, and we will follow that philosophy here. The observant reader will note that I have completely skipped over ionic bonding. Both hydrogen atoms feel like they have 2 valence electrons from their bond with oxygen. Thus oxygen now has 8 valence electrons: 4 from its unbonded electron and 4 more from its two covalent bonds (since each bond gives 2 electrons). The oxygen donated 1 electron to bond together with each hydrogen’s electron (note that the two bonds have the colors of both atoms, since each atom donated 1 electron to make up the bond). Oxygen (in group 16) began with 6 valence electrons while both of the hydrogen atoms (group 1) began with 1 valence electron. ![]() Returning to the Lewis diagram for water: By donating one electron into the bond and getting to feel both electrons from the bond, each of the atoms increases its valence electron count by 1 electron. A covalent bond occurs when two atoms each place one of their electrons into the space between them, thereby allowing both atoms to act as if both electrons are a part of their valence shell. The most common way for atoms to gain additional valence electrons is by sharing electrons and forming covalent bonds. The third and final fact we need is that every atom (except hydrogen or helium) wants to have 8 valence electrons. I have skipped over groups 3 through 12 on purpose-more on that below. The second fact is that elements in groups 1, 2, 13, 14, 15, 16, 17, and 18 have 1, 2, 3, 4, 5, 6, 7, and 8 valence electrons, which is the number of electrons they have in their outermost shell (compared to these outermost electrons, the innermost electrons barely have an effect and hence can be ignored). The group numbers are shown above the columns in the following periodic table. The first fact is a definition: the columns of the periodic table are labeled from 1 to 18, and elements in columns 1, 2, 3, …, 18 are said to be in group 1, 2, 3, …, 18. In order to do this, we need three basic chemistry facts. Let’s go through some examples to get a sense of what drawing a Lewis structure entails. In particular, Wolfram|Alpha will point out when there are multiple ways to draw a molecule rather than keeping you guessing on whether another answer is “as correct” as the given one. States interesting properties: Wolfram|Alpha draws your attention when neat things are happening inside of a molecule (special bond types, expanded valence shells, etc).Points out exceptions: Wolfram|Alpha teaches you how to correctly deal with these “special cases,” so you don’t fear them.(We give an in-depth explanation of different bonding types below.) Explains why bonds occur and distinguishes between bonding types: The interface determines which bonds should be single, double, or triple and why. This is truly at the heart of chemical bonding.It is completely self-contained: All relevant information (valence electron count, electronegativities of atoms, etc.) is inside of the steps if needed.The Step-by-step interface includes these features: Wolfram|Alpha now helps users understand the principles behind bonding and chemical structures. With these steps, users can go above and beyond just seeing what the Lewis structure of nitrogen dioxide (NO 2) looks like. With one click of a button, Wolfram|Alpha Pro users can access Step-by-step functionality that will guide them through the process of drawing a Lewis structure. For example, here are the Lewis structures of water and ethylene. The atoms (represented by letters) are connected by bonds (pairs of electrons represented by lines), with any “leftover” or unbonded electrons on each atom displayed as dots. ![]() Molecules are composed of atoms, bonds, and unbonded electrons. ![]() Thus, Wolfram|Alpha is expanding its Step-by-step interface into the realm of chemical bonding (with even more Step-by-step functionality coming soon). But as any good teacher will tell you, even more important than finding the answer is the procedure used to get that answer. Wolfram|Alpha now supports Lewis structures-diagrams that show both the bonded and unbonded electrons in a molecule. Bonding is pretty fundamental, as it determines the shape of a molecule, which in turn determines how a molecule behaves.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |