Lewis structural formulas formal charges

The curious reversal from the C+0 polarity expected on electronegativity grounds may be attributed to the formal charges (C and 0+) that are associated with the usual triple-bonded Lewis-structure formula. 

You may recall that we had to decide whether to draw the double bond between C and O or between C and Cl. We decided in favor of a carbon—oxygen double bond by applying the simple idea that multiple bonds most likely involve C, N, O, and S atoms. In this section, we will describe how you can use the concept of formal charge to determine the best Lewis formula. Formal charge is also a help in writing the skeleton structure of a molecule. 

Thus, (4.9a) gives the general condition for an idealized covalently bonded closed-shell Lewis-like duodectet structure (4.9b) with no formal charge on the central metal atom. (The more general conditions for coordinative [dative] ligands and other departures from the idealized Lewis-like formula will be discussed below.)... 

Now we will apply this formal-charge concept to the cyanate ion OCN We chose this example because many students incorrectly write the formula as CNO , and then try to use this as the atomic arrangement in the Lewis structure. Based on the number of electrons needed, the carbon should be the central atom. We will work this example using both the incorrect atom arrangement and the correct atom arrangement. Notice that in both structures all atoms have a complete octet. 

Q Draw and interpret Lewis, condensed, and line-angle structural formulas. Calculate formal charges. 

Draw Lewis structures for the nine isomers having molecular formula CsHgO, with all atoms having a zero formal charge. 

To calculate formal charges, use the completed Lewis structure and the following formula ... 

A Lewis formula can be written for BeCl2 that does satisfy the octet rule (see structure shown in the margin). Let us evaluate the formal charges for that formula ... 

A stepwise process is used to convert a molecular formula into a Lewis structure, a two-dimensional representation of a molecule (or ion) that shows the relative placement of atoms and distribution of valence electrons among bonding and lone pairs. When two or more Lewis structures can be drawn for the same relative placement of atoms, the actual structure is a hybrid of those resonance forms. Formal charges are often useful for determining the most important contributor to the hybrid. Electron-deficient molecules (central Be or B) and odd-electron species (free radicals) have less than an octet around the central atom but often attain an octet in reactions. In a molecule (or ion) with a central atom from Period 3 or higher, the atom can hold more than eight electrons by using d orbitals to expand its valence shell. 

When molten sulfur reacts with chlorine gas, a vile-smelling orange liquid forms that has an empirical formula of SCI. The structure of this compound has a formal charge of zero on all elements in the compound. Draw the Lewis structure for the vile-smelling orange liquid. 

Write a Lewis formula for the CH3NO isomer characterized by the structural unit indicated. None of the atoms in the Lewis structure should have a formal charge. 

Complete the following Lewis structures. Indicate any unshared pairs of electrons and formal charges. The formulas represent neutral molecules. 

Write a more stable contributing structure for each of the following. Use curved arrows to show how to transform the original Lewis formula to the new one. Be sure to specify formal charges, if any. 

Lewis dot formulas are the major means by which structural information is communicated in organic chemistry. These structural formulas show the atoms, bonds, location of unshared pairs, and formal charges. 

A new formula should be drawn to show the result of the electron shift(s). All formulas should be proper Lewis structures and should include formal charges as appropriate. The maximum number of valence electrons should not be exceeded for any atom in a formula. 

Lewis structures and any resonance structures for the ion with formula CH2NO2. Show all formal charges and lone pairs of electrons. 

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