Skip to main content

Introductory Chemistry - 1st Canadian Edition: Lewis Electron Dot Diagrams

Introductory Chemistry - 1st Canadian Edition
Lewis Electron Dot Diagrams
    • Notifications
    • Privacy
  • Project HomeNatural Sciences Collection: Anatomy, Biology, and Chemistry
  • Projects
  • Learn more about Manifold

Notes

Show the following:

  • Annotations
  • Resources
Search within:

Adjust appearance:

  • font
    Font style
  • color scheme
  • Margins
table of contents
  1. Cover
  2. Title Page
  3. Copyright
  4. Table Of Contents
  5. Acknowledgments
  6. Dedication
  7. About BCcampus Open Education
  8. Chapter 1. What is Chemistry
    1. Some Basic Definitions
    2. Chemistry as a Science
  9. Chapter 2. Measurements
    1. Expressing Numbers
    2. Significant Figures
    3. Converting Units
    4. Other Units: Temperature and Density
    5. Expressing Units
    6. End-of-Chapter Material
  10. Chapter 3. Atoms, Molecules, and Ions
    1. Acids
    2. Ions and Ionic Compounds
    3. Masses of Atoms and Molecules
    4. Molecules and Chemical Nomenclature
    5. Atomic Theory
    6. End-of-Chapter Material
  11. Chapter 4. Chemical Reactions and Equations
    1. The Chemical Equation
    2. Types of Chemical Reactions: Single- and Double-Displacement Reactions
    3. Ionic Equations: A Closer Look
    4. Composition, Decomposition, and Combustion Reactions
    5. Oxidation-Reduction Reactions
    6. Neutralization Reactions
    7. End-of-Chapter Material
  12. Chapter 5. Stoichiometry and the Mole
    1. Stoichiometry
    2. The Mole
    3. Mole-Mass and Mass-Mass Calculations
    4. Limiting Reagents
    5. The Mole in Chemical Reactions
    6. Yields
    7. End-of-Chapter Material
  13. Chapter 6. Gases
    1. Pressure
    2. Gas Laws
    3. Other Gas Laws
    4. The Ideal Gas Law and Some Applications
    5. Gas Mixtures
    6. Kinetic Molecular Theory of Gases
    7. Molecular Effusion and Diffusion
    8. Real Gases
    9. End-of-Chapter Material
  14. Chapter 7. Energy and Chemistry
    1. Formation Reactions
    2. Energy
    3. Stoichiometry Calculations Using Enthalpy
    4. Enthalpy and Chemical Reactions
    5. Work and Heat
    6. Hess’s Law
    7. End-of-Chapter Material
  15. Chapter 8. Electronic Structure
    1. Light
    2. Quantum Numbers for Electrons
    3. Organization of Electrons in Atoms
    4. Electronic Structure and the Periodic Table
    5. Periodic Trends
    6. End-of-Chapter Material
  16. Chapter 9. Chemical Bonds
    1. Lewis Electron Dot Diagrams
    2. Electron Transfer: Ionic Bonds
    3. Covalent Bonds
    4. Other Aspects of Covalent Bonds
    5. Violations of the Octet Rule
    6. Molecular Shapes and Polarity
    7. Valence Bond Theory and Hybrid Orbitals
    8. Molecular Orbitals
    9. End-of-Chapter Material
  17. Chapter 10. Solids and Liquids
    1. Properties of Liquids
    2. Solids
    3. Phase Transitions: Melting, Boiling, and Subliming
    4. Intermolecular Forces
    5. End-of-Chapter Material
  18. Chapter 11. Solutions
    1. Colligative Properties of Solutions
    2. Concentrations as Conversion Factors
    3. Quantitative Units of Concentration
    4. Colligative Properties of Ionic Solutes
    5. Some Definitions
    6. Dilutions and Concentrations
    7. End-of-Chapter Material
  19. Chapter 12. Acids and Bases
    1. Acid-Base Titrations
    2. Strong and Weak Acids and Bases and Their Salts
    3. Brønsted-Lowry Acids and Bases
    4. Arrhenius Acids and Bases
    5. Autoionization of Water
    6. Buffers
    7. The pH Scale
    8. End-of-Chapter Material
  20. Chapter 13. Chemical Equilibrium
    1. Chemical Equilibrium
    2. The Equilibrium Constant
    3. Shifting Equilibria: Le Chatelier’s Principle
    4. Calculating Equilibrium Constant Values
    5. Some Special Types of Equilibria
    6. End-of-Chapter Material
  21. Chapter 14. Oxidation and Reduction
    1. Oxidation-Reduction Reactions
    2. Balancing Redox Reactions
    3. Applications of Redox Reactions: Voltaic Cells
    4. Electrolysis
    5. End-of-Chapter Material
  22. Chapter 15. Nuclear Chemistry
    1. Units of Radioactivity
    2. Uses of Radioactive Isotopes
    3. Half-Life
    4. Radioactivity
    5. Nuclear Energy
    6. End-of-Chapter Material
  23. Chapter 16. Organic Chemistry
    1. Hydrocarbons
    2. Branched Hydrocarbons
    3. Alkyl Halides and Alcohols
    4. Other Oxygen-Containing Functional Groups
    5. Other Functional Groups
    6. Polymers
    7. End-of-Chapter Material
  24. Chapter 17. Kinetics
    1. Factors that Affect the Rate of Reactions
    2. Reaction Rates
    3. Rate Laws
    4. Concentration–Time Relationships: Integrated Rate Laws
    5. Activation Energy and the Arrhenius Equation
    6. Reaction Mechanisms
    7. Catalysis
    8. End-of-Chapter Material
  25. Chapter 18. Chemical Thermodynamics
    1. Spontaneous Change
    2. Entropy and the Second Law of Thermodynamics
    3. Measuring Entropy and Entropy Changes
    4. Gibbs Free Energy
    5. Spontaneity: Free Energy and Temperature
    6. Free Energy under Nonstandard Conditions
    7. End-of-Chapter Material
  26. Appendix A: Periodic Table of the Elements
  27. Appendix B: Selected Acid Dissociation Constants at 25°C
  28. Appendix C: Solubility Constants for Compounds at 25°C
  29. Appendix D: Standard Thermodynamic Quantities for Chemical Substances at 25°C
  30. Appendix E: Standard Reduction Potentials by Value
  31. Glossary
  32. About the Authors
  33. Versioning History

Lewis Electron Dot Diagrams

Learning Objectives

  1. Draw a Lewis electron dot diagram for an atom or a monatomic ion.

In almost all cases, chemical bonds are formed by interactions of valence electrons in atoms. To facilitate our understanding of how valence electrons interact, a simple way of representing those valence electrons would be useful.

A Lewis electron dot diagram (or electron dot diagram or a Lewis diagram or a Lewis structure) is a representation of the valence electrons of an atom that uses dots around the symbol of the element. The number of dots equals the number of valence electrons in the atom. These dots are arranged to the right and left and above and below the symbol, with no more than two dots on a side. (It does not matter what order the positions are used.) For example, the Lewis electron dot diagram for hydrogen is simply:

\LARGE \ce{\Lewis{0.,H}}

Because the side is not important, the Lewis electron dot diagram could also be drawn as follows:

\Lewis{2.,H}\hspace{10 mm}\text{or}\hspace{10 mm}\Lewis{4.,H}\hspace{10 mm}\text{or}\hspace{10 mm}\Lewis{6.,H}

The electron dot diagram for helium, with two valence electrons, is as follows:

\LARGE \ce{\Lewis{0:,He}}

By putting the two electrons together on the same side, we emphasize the fact that these two electrons are both in the 1s subshell; this is the common convention we will adopt, although there will be exceptions later. The next atom, lithium, has an electron configuration of 1s22s1, so it has only one electron in its valence shell. Its electron dot diagram resembles that of hydrogen, except the symbol for lithium is used:

\LARGE \ce{\Lewis{0.,Li}}

Beryllium has two valence electrons in its 2s shell, so its electron dot diagram is like that of helium:

\LARGE \Lewis{0:,Be}

The next atom is boron. Its valence electron shell is 2s22p1, so it has three valence electrons. The third electron will go on another side of the symbol:

\LARGE \Lewis{0:2.,B}

Again, it does not matter on which sides of the symbol the electron dots are positioned.

For carbon, there are four valence electrons, two in the 2s subshell and two in the 2p subshell. As usual, we will draw two dots together on one side, to represent the 2s electrons. However, conventionally, we draw the dots for the two p electrons on different sides. As such, the electron dot diagram for carbon is as follows:

\huge \Lewis{0:2.4.,C}

With nitrogen, which has three p electrons, we put a single dot on each of the three remaining sides:

\huge \Lewis{0:2.4.6.,N}

For oxygen, which has four p electrons, we now have to start doubling up on the dots on one other side of the symbol. When doubling up electrons, make sure that a side has no more than two electrons.

\huge \Lewis{0:2:4.6.,O}

Fluorine and neon have seven and eight dots, respectively:

\LARGE \Lewis{0:2:4:6.,F}\hspace{10mm}\Lewis{0:2:4:6:,Ne}

With the next element, sodium, the process starts over with a single electron because sodium has a single electron in its highest-numbered shell, the n = 3 shell. By going through the periodic table, we see that the Lewis electron dot diagrams of atoms will never have more than eight dots around the atomic symbol.

Example 9.1

Problem

What is the Lewis electron dot diagram for each element?

  1. aluminum
  2. selenium

Solution

  1. The valence electron configuration for aluminum is 3s23p1. So it would have three dots around the symbol for aluminum, two of them paired to represent the 3s electrons:

    \LARGE \Lewis{0:2.,Al}

  2. The valence electron configuration for selenium is 4s24p4. In the highest-numbered shell, the n = 4 shell, there are six electrons. Its electron dot diagram is as follows:

    \huge \Lewis{0:2.4.6:,Se}

Test Yourself

What is the Lewis electron dot diagram for each element?

  1. phosphorus
  2. argon

Answer

\LARGE \Lewis{0:2.4.6.,P}\hspace{10mm}\Lewis{0:2:4:6:,Ar}

For atoms with partially filled d or f subshells, these electrons are typically omitted from Lewis electron dot diagrams. For example, the electron dot diagram for iron (valence shell configuration 4s23d6) is as follows:

\LARGE \Lewis{0:,Fe}

Elements in the same column of the periodic table have similar Lewis electron dot diagrams because they have the same valence shell electron configuration. Thus the electron dot diagrams for the first column of elements are as follows:

\large \Lewis{0.,H}\hspace{10mm}\Lewis{0.,Li}\hspace{10mm}\Lewis{0.,Na}\hspace{10mm}\Lewis{0.,K}\hspace{10mm}\Lewis{0.,Rb}\hspace{10mm}\Lewis{0.,Cs}\hspace{10mm}

Monatomic ions are atoms that have either lost (for cations) or gained (for anions) electrons. Electron dot diagrams for ions are the same as for atoms, except that some electrons have been removed for cations, while some electrons have been added for anions. Thus in comparing the electron configurations and electron dot diagrams for the Na atom and the Na+ ion, we note that the Na atom has a single valence electron in its Lewis diagram, while the Na+ ion has lost that one valence electron:

\begin{array}{lll} \text{Lewis dot diagram:}&\Lewis{0.,Na}&\ce{Na^+} \\ \text{Electron configuration:}&\ce{[Ne]}3s^1&\ce{[Ne]} \end{array}

Technically, the valence shell of the Na+ ion is now the n = 2 shell, which has eight electrons in it. So why do we not put eight dots around Na+? Conventionally, when we show electron dot diagrams for ions, we show the original valence shell of the atom, which in this case is the n = 3 shell and empty in the Na+ ion.

In making cations, electrons are first lost from the highest numbered shell, not necessarily the last subshell filled. For example, in going from the neutral Fe atom to the Fe2+ ion, the Fe atom loses its two 4s electrons first, not its 3d electrons, despite the fact that the 3d subshell is the last subshell being filled. Thus we have:

\begin{array}{lll} \text{Lewis dot diagram:}&\Lewis{0:,Fe}&\ce{Fe^{2+}} \\ \text{Electron configuration:}&\ce{[Ar]}4s^23d^6&\ce{[Ar]}3d^6 \end{array}

Anions have extra electrons when compared to the original atom. Here is a comparison of the Cl atom with the Cl− ion:

\begin{array}{lll} \text{Lewis dot diagram:}&\Lewis{0.2:4:6:,Cl}&\ce{\Lewis{0:2:4:6:,Cl}^-} \\ \text{Electron configuration:}&\ce{[Ne]}3s^23p^5&\ce{[Ne]}3s^23p^6 \end{array}

Example 9.2

Problem

What is the Lewis electron dot diagram for each ion?

  1. Ca2+
  2. O2−

Solution

  1. Having lost its two original valence electrons, the Lewis electron dot diagram is just Ca2+.
  2. The O2− ion has gained two electrons in its valence shell, so its Lewis electron dot diagram is as follows:

    \large \ce{\Lewis{0:2:4:6:,O}}^{2-}

Test Yourself

The valence electron configuration of thallium, whose symbol is Tl, is 6s25d106p1. What is the Lewis electron dot diagram for the Tl+ ion?

Answer

\ce{\Lewis{0:,Tl}^+}

Key Takeaways

  • Lewis electron dot diagrams use dots to represent valence electrons around an atomic symbol.
  • Lewis electron dot diagrams for ions have fewer (for cations) or more (for anions) dots than the corresponding atom.

Exercises

Questions

  1. Explain why the first two dots in a Lewis electron dot diagram are drawn on the same side of the atomic symbol.
  2. Is it necessary for the first dot around an atomic symbol to go on a particular side of the atomic symbol?
  3. What column of the periodic table has Lewis electron dot diagrams with two electrons?
  4. What column of the periodic table has Lewis electron dot diagrams that have six electrons in them?
  5. Draw the Lewis electron dot diagram for each element.
    1. strontium
    2. silicon
  6. Draw the Lewis electron dot diagram for each element.
    1. krypton
    2. sulfur
  7. Draw the Lewis electron dot diagram for each element.
    1. titanium
    2. phosphorus
  8. Draw the Lewis electron dot diagram for each element.
    1. bromine
    2. gallium
  9. Draw the Lewis electron dot diagram for each ion.
    1. Mg2+
    2. S2−
  10. Draw the Lewis electron dot diagram for each ion.
    1. In+
    2. Br−
  11. Draw the Lewis electron dot diagram for each ion.
    1. Fe2+
    2. N3−
  12. Draw the Lewis electron dot diagram for each ion.
    1. H+
    2. H−

Answers

  1. The first two electrons in a valence shell are s electrons, which are paired.
  1. The second column of the periodic table.
    1. \LARGE \Lewis{0:,Sr}
    2. \huge \Lewis{0.2.4.6.,Si}
    1. \LARGE \Lewis{0:,Ti}
    2. \huge \Lewis{0:2.4.6.,P}
    1. \ce{Mg^{2+}}
    2. \LARGE \ce{\Lewis{0:2:4:6:,S}^{2-}}
    1. \ce{Fe}^{2+}
    2. \LARGE \ce{\Lewis{0:2:4:6:,N}^{3-}}

Annotate

Next Chapter
Electron Transfer: Ionic Bonds
PreviousNext
Chemistry

Copyright © 2014

                                by Jessie A. Key

            Introductory Chemistry - 1st Canadian Edition by Jessie A. Key is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.
Powered by Manifold Scholarship. Learn more at
Opens in new tab or windowmanifoldapp.org