Chemical Bonding - a review

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For your benefit, do this.

Use subheadings to create a summary of concepts used in chemical bonding.

Chemical Bonding - a revew

This quiz will cover the following topic:

Covalent and ionic substances
Covalent and ionic bonds
Lewis symbols and Lewis dot structues
The octet rule and formal charges
Exceptions to the octet rule
Covalent bond and ionic bond
Count number of unshared valence electron pairs
Resonance Structures
Calculation of lattice energy
Calculate enthalpy of reaction from bond energy or from energy of formation
Use of Hess law for the calculation of various thermochemical energy
Dipole moment
Dipole moment and shape of molecules

Here are four problems related to Lewis dot structure, resonance, and formal charges. The last question is intended to direct you to a more realistic problem.

Confidence Building Questions

Give the Lewis symbol for Be.

Skill: Give the Lewis symbol for one of the main group element
How many valence electrons are there for the element S?

Skill: Evaluate numbers of valence electrons from group numbers and from electronic configurations. Elements O, S, Se, and Te all have 6 valence electrons.
Draw the resonance structures of NO₂.

Solution: Here are some suggested example
```
  .      .     ..     ..
  N      N     N      N
/  \\  // \   / \\  // \
O   O  O   O O   O  O   O
             .          .
```
The paired electrons are not shown here.
What is the formal charge of N in the dot structure
. N / \\ O O

Skill: Evaluate the formal charge of any atom of any dot structure.
What is the formal charge for the resonance structure having the odd electron on the oxygen atom?
What is the bond order for the N-O bond in NO₂?

Discussion: Four resonance structure have been given, and all indicate a bond order of 1.5 for
[O-N=O] <=> [O=N-O].
What quantities are required in order to calculate the latice energy of NaCl?

Skill: Solving real-world problems requires you to know what information to look for before the problem is solvable. This is one of those problems.
In an exercise or an open-book test, we can ask you to evaluate the lattice energy of a salt, and you need to find the various data. Since the CAcT quiz is an open-book test, this type of problem should have been given, but you will not have this type of problem in this quiz.
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