Writing Lewis Formulas

The objective of this section is to become comfortable with writing Lewis structural formulas. We can only predict the Lewis structures of simple molecules. 

Other complex stmctures require complicated analysis and predictions based 

determine the main stmctural make up of the molecule, such as guessing which atom will be the central atom of the molecule. The central atom of the molecule is usually the atom with the lowest electronegativity. 

determine the total number of valence (outermost) electrons. 

determine the distribution of those valence electrons so as to complete the octet of the atoms that are around or bonded to the central atom. 

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The Lewis rules are relatively straightforward easiest to master and the most familiar You will find that your ability to write Lewis formulas increases rapidly with experience Get as much practice as you can early m the course Success m organic chemistry depends on writing correct Lewis structures... 

For now, we restrict our discussion to compounds of the representative elements. The octet rule alone does not let us write Lewis formulas. We still must decide how to place the electrons around the bonded atoms—that is, how many of the available valence electrons are bonding electrons (shared) and how many are unshared electrons (associated with only one atom). A pair of unshared electrons in the same orbital is called a lone pair. A simple mathematical relationship is helpful here ... 

A very common error in writing Lewis formulas is showing the wrong number of electrons. Always make a final check to be sure that the Lewis formula you write shows the same number of electrons you calculated as A. 

We follow the stepwise procedure that was just presented for writing Lewis formulas. Solution... 

Write Lewis formulas for CH4 and SiH4 explain the similarity. 

Write Lewis formulas for the fluorine molecule and for sodium fluoride. Describe the nature of the chemical bonding involved in each substance. 

Write Lewis formulas for butane, CH3CH2CH2CH3, and propane, CH,CH7CH,. Describe the nature... 

Careful examination of the ozone molecule indicates that the two outer oxygens are the same distance from the central oxygen. Write Lewis formulas or resonance structures that are consistent with this finding. 

Write Lewis formulas for three different atomic arrangements with the molecular formula HCNO. Indicate aU formal charges. Predict which arrangement is likely to be the least stable and justify your selection. 

The electrons in the outer shell, or valence shell, of an atom are the electrons involved in bonding. In most of our discussion of covalent bonding, we will focus attention on these electrons. Valence shell electrons are those that were not present in the preceding noble gas, ignoring filled sets of d and / orbitals. Lewis formulas show the number of valence shell electrons in a polyatomic molecule or ion (Sections 7-4 through 7-7). We will write Lewis formulas for each molecule or polyatomic ion we discuss. The theories introduced in this chapter apply equally well to polyatomic molecules and to ions. 

As the name implies, the interhalogens are compounds that contain two halogens. Write Lewis formulas and three-dimensional structures for the following. Name the electronic and molecular geometries of each, (a) BrFj ... 

Write Lewis formulas for molecular oxygen and ozone. Assuming that all of the valence electrons in the oxygen atoms are in hybrid orbitals, what would be the hybridization of the oxygen atoms in each substance Prepare sketches of the molecules. 

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