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Electronegativity and Electron Affinity

The degree of ionic character of a compound is determined by comparing the electronegativities of the species involved. The greater the difference in electronegativity, the more ionic the compound. Electron affinity is related to the release of energy whenever an electron tends to get added to an atom. These two properties are often known to be interrelated but they are not interchangeable. Both electronegativity and electron affinity deal with the movement of the electrons. However, electronegativity is the result of the property of attraction, while electron affinity is the result of the change in energy.

Time: 7:12 min.

Topics: What is it and the Pauling Scale; Why does it matter?; Patterns; Calculation (covalent vs ionic)

 

 

Classification of Ionic Character

The degree of ionic character of a compound is determined by comparing the electronegativities of the species involved. The greater the difference in electronegativity, the more ionic the compound.

Time: 8:18 min.

Topics: Classification of bonds by Difference in Electronegativity; Polar Covalent Bonds; Example Problems

 

 

Formal Charges

A formal charge (FC) is the charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity.

Time: 5:02 min.

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Formal Charges Example

Time: 5:16 min.

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Endothermic and Exothermic

An exothermic process releases heat, causing the temperature of the immediate surroundings to rise. An endothermic process absorbs heat and cools the surroundings.

Time: 7:48 min.

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Example 9.13

Time: 1:26 min.

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Writing Lewis Structures

A Lewis Structure is a very simplified representation of the valence shell electrons in a molecule. It is used to show how the electrons are arranged around individual atoms in a molecule. Electrons are shown as "dots" or for bonding electrons as a line between the two atoms.

Time: 6:08 min.

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Resonance & Resonance Structures

Resonance is a way of describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by a single Lewis formula. A molecule or ion with such delocalized electrons is represented by several resonance structures. The nuclear skeleton of the Lewis Structure of these resonance structures remains the same, only the electron locations differ.

Time: 7:48 min.

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Exceptions to the Octet Rule

The octet rule is subject to three basic exceptions: Molecules containing an odd number of electrons, such as NO; SF₆ molecules in which one or more atoms have more than eight electrons; and. Molecules contain more atoms with less than eight electrons, like BCl₃.

Time: 9:54 min.

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