11. Bonding & Molecular Structure

Formal Charge

Resonance Structures and Formal Charge

Drawing Lewis Structures for Molecules: Considering Formal Charge

The sum of all formal charges in a neutral molecule must be zero.

The sum of all formal charges in an ion must be equal to ionic charge.

The sum of all formal charges in an ion must be equal to zero.

Correct, the sum of all formal charges in an ion must be equal to the ionic charge.

Small (or zero) formal charges on individual atoms are generally better than larger ones.

When formal charge cannot be avoided, negative formal charge should reside on the most electronegative atom.

 Review the rules for determining formal charges. 

Formal Charge Example 1

Electronegativity generally increases across a period in the periodic table.

Electronegativity tends to increase diagonally from the lower left in Column 1A to the upper right in Column 7A of the periodic table.

Electronegativity generally decreases down a column in the periodic table.

Fluorine is the most electronegative atom.

Francium is the least electronegative atom (sometimes called the most electropositive).

Correct, electronegativity tends to increase diagonally from the lower left to the upper right (Column 7A) of the periodic table.

 Electronegativity is the ability of an atom to attract electrons to itself in a chemical bond. 

Which is the best electron-dot structure for the thiosulfate ion (S2O3 2-) based on the rules of formal charge? (LO 7.16)
(a) 
(b) 
(c) 
(d)

In N2O, nitrogen is the central atom and the oxygen atom is terminal.
In OF2, however, oxygen is the central atom. Use formal
charges to explain why.

What are the formal charges of the atoms shown in red?
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/45788d989d076913-1659962441606.jpg" alt="" />

How to Calculate Formal Charges from Lewis Structures (Easy Method)

Formal Charges: Calculating Formal Charge

Which element within the thiocyanate ion possesses a negative charge?<img src="https://static.studychannel.pearsonprd.tech/courses/general-chemistry/thumbnails/images/637a528e"class="fr-fic fr-dii">a) Cb) Sc) Nd) All of theme) None of them

Which one of these statements about formal charge is true?
(a) Formal charge is the same as oxidation number. (b) To
draw the best Lewis structure, you should minimize formal
charge. (c) Formal charge takes into account the different
electronegativities of the atoms in a molecule. (d) Formal
charge is most useful for ionic compounds. (e) Formal charge
is used in calculating the dipole moment of a diatomic
molecule.

How to Determine the Most Stable Lewis Structure Practice Problems, Examples, Questions, Summary

Consider the Lewis structure shown below.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/4e6a544207b653f0-1660920043522.jpg" alt="" />
(a) Does the Lewis structure depict a neutral molecule or an
ion? If it is an ion, what is the charge on the ion?

What is the charge on the ion

What are the formal charges of the atoms shown in red?

Calculate the formal charges for each of the oxygen atoms within the nitrite ion, NO2–.<img src="https://static.studychannel.pearsonprd.tech/courses/general-chemistry/thumbnails/images/8c381aa4"class="fr-fic fr-dii"><img src="https://lightcat-files.s3.amazonaws.com/problem_images/31c670688c2c3a1c-1608580741699.jpg"class="fr-fic fr-dii">

Calculate the formal charge of the carbon atom within a carbon monoxide molecule.<img src="https://static.studychannel.pearsonprd.tech/courses/general-chemistry/thumbnails/images/93b852ee"class="fr-fic fr-dii">a) –1b) +2c) 0d) +e) –2

In the Lewis structure shown here, A, D, E, Q, X, and Z represent 
elements in the first two rows of the periodic table. 
Identify all six elements so that the formal charges of all atoms 
are zero.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/36af7a201c36b5bf-1668006530214.jpg" alt="" />

Lewis Theory VIII:  Formal Charge

Consider the Lewis structure for the polyatomic oxyanion 
shown here, where X is an element from the third period 
1Na - Ar2. By changing the overall charge, n, from 1- to 
2- to 3- we get three different polyatomic ions. For each of 
these ions (b) determine the formal charge of the central atom, X; 
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/60fe25b3c60e7f2c-1660919614076.jpg" alt="" />

The following three Lewis structures can be drawn for N2O:
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/9c2568b41d595cf2-1660915587896.jpg" alt="" />
(a) Using formal charges, which of these three resonance
forms is likely to be the most important?

Use formal charges to identify the better Lewis structure.

Net Charge is the sum of individual formal charges within a compound.

Based on calculated formal charges, determine the overall charge (net charge) for the following compound.<img src="https://static.studychannel.pearsonprd.tech/courses/general-chemistry/thumbnails/images/f0ec2738"class="fr-fic fr-dii">a) –3b) +4c) +1d) –1e) +2

In the vapor phase, BeCl2 exists as a discrete molecule.
(c) On the basis of the formal charges, which Lewis structure is expected to be dominant for BeCl2?<img src="https://lightcat-files.s3.amazonaws.com/problem_images/ecd6963f3fd5335e-1660911470550.jpg" alt="" />

Formal Charge and Lewis Structures

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Lewis Dot Structures: Neutral Compounds

Lewis Dot Structures or Electron Dot Structures&nbsp;are diagrams that show how elements in a molecule use their valence electrons to form bonds.&nbsp;

Average Bond Order

Average Bond Order represents the average number of chemical bonds between a pair of bond elements.

Lewis Dot Structures: Ions

Lewis Dot Structures of Ions involves losing or gaining valence electrons to draw the most likely structure.&nbsp;

Octet Rule

The&nbsp;Octet Rule states that main-group elements will generally form enough bonds to obtain 8 electrons in their valence shell.&nbsp;

Lewis Dot Symbols

Lewis Dot Symbols represent the outer shell electrons of an element.&nbsp;

Lewis Dot Structures: Sigma & Pi Bonds

Sigma Bonds directly connect element together, while Pi Bonds provide insulation and protection for those bonds.&nbsp;

Lewis Dot Structures: Exceptions

Lewis Dot Structure Exceptions&nbsp;happen when the central element violates the Octet Rule.

Born Haber Cycle

In the Born-Haber Cycle, ionic solids are created through the ionization and eventual combination of elements.&nbsp;

Coulomb's Law

Coulomb's Law is used to determine the forces experienced by charged particles.&nbsp;

Chemical Bonds

A chemical bond is the connection&nbsp;of different elements through the sharing, transferring or pooling of electrons.&nbsp;

Resonance Structures

Resonance Structures are used to represent the different possible bonding arrangements of a molecule.

Lewis Dot Structures: Acids

Drawing the Lewis Dot Structure of Acids&nbsp;involves first drawing the polyatomic anion and then attaching the H+ ion.&nbsp;

Formal Charge is the charge given to an element within a molecule when assuming equal sharing of electrons between bonded elements.&nbsp;

Bond Energy

Bond Energy is the amount of energy stored within a chemical bond.

Lattice Energy

Lattice Energy&nbsp;is the estimate for the strength of ionic bonds.&nbsp;

Dipole Moment

Dipole arrows are used anytime a molecule possesses a dipole moment, which happens when a molecule is polar.&nbsp;