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Understanding Chemical Bonding and its Role in Climate Change, Summaries of Chemistry

An in-depth exploration of chemical bonding concepts, including ionic, covalent, and metallic bonds, Lewis structures, electronegativity, and polar bonds. It also discusses the relationship between chemical bonding and the greenhouse effect.

Typology: Summaries

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2/16/2018
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Ch. 4 - Chemical Bonding:
Understanding Climate Change
Chapter Outline
4.1 Types of Chemical Bonds
4.2 Naming Compounds and Writing
Formulas
4.3 Lewis Structures
4.4 Electronegativity, Unequal Sharing,
and Polar Bonds
4.5 Vibrating Bonds and the Greenhouse Effect
4.6 Resonance
4.7 Formal Charge: Choosing among Lewis Structures
4.8 Exceptions to the Octet Rule
4.8 The Lengths and Strengths of Covalent Bonds
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Download Understanding Chemical Bonding and its Role in Climate Change and more Summaries Chemistry in PDF only on Docsity!

Ch. 4 - Chemical Bonding:

Understanding Climate Change

Chapter Outline

4.1 Types of Chemical Bonds  4.2 Naming Compounds and Writing Formulas  4.3 Lewis Structures  4.4 Electronegativity, Unequal Sharing, and Polar Bonds  4.5 Vibrating Bonds and the Greenhouse Effect  4.6 Resonance  4.7 Formal Charge: Choosing among Lewis Structures  4.8 Exceptions to the Octet Rule  4.8 The Lengths and Strengths of Covalent Bonds

Ionic Covalent Metallic

Types of Chemical Bonds

 Types of chemical bonds:

  • Ionic Bond – electrons transferred: chemical bond resulting from the electrostatic attraction of a cation for an anion.
  • Covalent Bond – chemical bond that results from a sharing of outermost electrons.
  • Metallic Bond – chemical bond consisting of the nuclei of metal atoms surrounded by a “sea” of shared electrons.

Chemical Bonds

Lattice Energy (U)

  • As charges increase, so does the lattice energy
  • As the distance between ions decreases, the lattice energy increases
  • The energy released when one mole of an ionic compound forms from its free ions in the gas phase.

Covalent Bonds

H 2

Metallic Bonds

Cu = [Ar]3d^10 4s^1

4s^1

3d^10

  ^ ^ 

Bond Type Summary

1A ns^11 2A ns^22 3A (^) ns^2 np^13 4A (^) ns^2 np^24 5A (^) ns^2 np^35 6A (^) ns^2 np^46 7A (^) ns^2 np^57 Group e-^ configuration # of valence e- Lewis Dot Symbol Lewis Symbols and the Periodic Table Lewis Symbols and the Periodic Table Unpaired dots = bonding capacity. Main Group Elements: Members of same family have same number of valence electrons, and similar bonding capacities.

[Ne]3s^1 [Ne] Na Na+^ + e

[Ne]3s^2 3p^5 [Ne]3s^2 3p^6 = [Ar] e

  • Cl^ Na +

Lewis Structures of Ionic Compounds

Cl Na

+ Cl-

Cl

Sample Exercise 4.8 (Modified)

Draw the Lewis symbols of the monatomic ions formed by calcium and oxygen. Then draw the Lewis structure of calcium oxide (CaO).

  1. Sum up the total number of valence electrons (use the group number), and calculate the number of pairs.
  2. Connect the atoms together so that each atom has an octet (except H). You may have to form multiple bonds.

Guidelines for Drawing Lewis Structures

(updated later on with the concept of “formal charge”) Double bond – two atoms share two pairs of electrons Triple bond – two atoms share three pairs of electrons C 2 H 2

CO 2

Multiple Bonds – sharing more than one pair of electrons H 2 CO N 2

Lewis Structures of Charged Species ClO

NO 2

Electronegativity, Unequal Sharing, and Polar BondsElectronegativity ():

  • Ability of an atom to attract bonding electrons.
  • Periodic trend similar to ionization energy.

Electro-

negativities

Polar Covalent Bonds - Unequal sharing of electrons resulting in an uneven distribution of charge. Difference Bond Type Covalent  2 Ionic 0.4 < EN < 2 Polar Covalent

Cl 2

HCl

NaCl

Electronegativity Trends

 As seen previously, electronegativity increases moving up to the right in the periodic table. (Noble gases not included.)  Bond polarity increases as ΔEN increases. ΔEN = 1.9 0.9 0.7 0.

Sample Exercise 4.

Rank, in order of increasing polarity, the bonds formed between - O and C Cl and Ca N and S O and Si Are any of these bonds considered ionic?

Chapter Outline

 4.1 Types of Chemical Bonds  4.2 Naming Compounds and Writing Formulas  4.3 Lewis Structures  4.4 Electronegativity, Unequal Sharing, and Polar Bonds  4.5 Vibrating Bonds and the Greenhouse Effect  4.6 Resonance  4.7 Formal Charge: Choosing among Lewis Structures  4.8 Exceptions to the Octet Rule  4.8 The Lengths and Strengths of Covalent Bonds 2 8

Sample Exercise 4.13: Drawing Resonance Structures Draw all the resonance structures of the nitrate ion. Resonance in Organic Compounds 3 2 Benzene = C 6 H 6 and it forms a ring

Chapter Outline

 4.1 Types of Chemical Bonds  4.2 Naming Compounds and Writing Formulas  4.3 Lewis Structures  4.4 Electronegativity, Unequal Sharing, and Polar Bonds  4.5 Vibrating Bonds and the Greenhouse Effect  4.6 Resonance  4.7 Formal Charge: Choosing among Lewis Structures  4.8 Exceptions to the Octet Rule  4.8 The Lengths and Strengths of Covalent Bonds 3 3

 Three possible Lewis structures. Which one is

best?

Formal charge (FC): FC = # valence electrons – [ (# lone pair e-) + ½ (# shared)] 3 4

Formal Charge and Lewis Structures

Practice: Formal Charge

What is the most likely Lewis structure for CO 2?

  1. For neutral molecules, a Lewis structure in which there are no formal charges is preferable to one in which formal charges are present.
  2. Lewis structures with large formal charges are less plausible than those with small formal charges.
  3. Among Lewis structures having similar distributions of formal charges, the most plausible structure is the one in which negative formal charges are placed on the more electronegative atoms.

Summary: Formal Charge and Lewis Structures

A way to decide which Lewis Structure, out of several possibilities, that’s the most stable and therefore the most likely.

Chapter Outline

 4.1 Types of Chemical Bonds  4.2 Naming Compounds and Writing Formulas  4.3 Lewis Structures  4.4 Electronegativity, Unequal Sharing, and Polar Bonds  4.5 Vibrating Bonds and the Greenhouse Effect  4.6 Resonance  4.7 Formal Charge: Choosing among Lewis Structures  4.8 Exceptions to the Octet Rule  4.8 The Lengths and Strengths of Covalent Bonds 3 9

1. The Incomplete Octet (Central atom in Group 3A) e.g. BF 3

Exceptions to the Octet Rule