The Lewis Structure Explorer

November 18, 2020
Teaching & LearningSarah Wegwerth
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Optional pre-lesson on Lewis structures at bottom of page

Introduction

Welcome! We are excited to have you use our new explorer that combines physical objects and digital technology to provide a multisensory exploration of the sub-microscopic world of chemistry.

You may be wondering what is this and how does it work?

To build chemical structures you will be placing the magnetic pieces on the white board. Then, through the magic of computer vision, the webcam tracks what is happening on the board and the explorer provides audio feedback. For example, place a hydrogen atom (H) on the board and listen to the explorer.

After placing the H, you should have heard “Hydrogen added to board. The electron count is one.” This is the number of valence electrons hydrogen has. As you build Lewis structures, you must account for all of the valence electrons contained by the atoms included in the molecule, as indicated by the electron count. The valence electrons are represented by either bonds or lone pairs of electrons. You know this has been accomplished when the electron count is zero.

To reveal warnings about an atom, you can also use the hint token which is shaped like a tear drop with a question mark and “hint” in braille. For example, place the tear drop so that the point is touching the hydrogen atom and listen.

You should have heard “Warnings on hydrogen. Incorrect formal charge. Less than a duet.” As you complete the lesson below, experiment with bonds, lone pairs, and charges until all the warnings are corrected and you hear “no warnings on atom”. Remember, there is no pressure to get it right the first time. Use this explorer to learn through trial and error and discover the common bonding patterns of chemical compounds.

Lewis Structure Explorer Tutorial

In this section you will learn how to use the Lewis Structure Explorer.

1. Learn how to make bonds by following the steps below to build a Lewis structure of H2.

  • a. Clear the board.
  • b. Place two hydrogen atoms (H) on the board. The electron count should be 2.
  • c. Connect the two H atoms using a single bond. Notice the short side of the bond has a curve so that it can fit tight against an atom. Make sure the bond is connected to each atom by placing them in the curve. Once the atoms are successfully bonded you should hear “You’ve made H2, hydrogen” and the electron count should be at zero.

2. Learn how to add lone pairs and use the hint token by following the steps below to build a Lewis structure of Cl2.

  • a. Clear the board.
  • b. Place two chlorine atoms (Cl) on the board and listen for the electron count.
  • c. Connect the two chlorine atoms by a single bond.
  • d. Notice the electron count decreased to 12 because 2 electrons were used to make the bond.
  • e. Place the warning token so the point touches one of the chlorines. Since chlorine needs to fill an octet, you should hear “warnings on chlorine, incorrect formal charge, less than octet.”
  • f. Add lone pairs of electrons to that chlorine atom until it has an octet of electrons and it says “no warnings on chlorine” when the hint token is pointed to it. Notice, the lone pair pieces have a side that is curved and can fit tight against the atoms.
  • g. Add lone pairs to the other chlorine to complete the octet and so the electron count is zero.
  • h. You have made the correct structure when you hear “You’ve made Cl2, chlorine.”

Congrats! You have completed the introduction and are now ready to explore bonding patterns!

Learning the rules for bonding

In this section you will build a variety of Lewis structures and identify the bonding pattern of the most commonly used atoms.

3. Follow the instructions below and build a Lewis structure of HCl then fill in the blanks in the sentences below.

  • a. Clear the board.
  • b. Place one hydrogen atom (H) and one chlorine atom (Cl) on the board.
  • c. Add bonds and or lone pairs of electrons until the electron count is zero.
  • d. Use the hint token to check your work
  • e. You have made the correct structure when you hear “you’ve made HCl, hydrogen chloride.”
  • f. Fill in the blanks: Hydrogen usually has _____ bonds and _____ lone pairs. Chloride usually has _____ bonds and _____ lone pairs.

4. Follow the instructions below and build a Lewis structure of H2O then fill in the blanks in the sentence below.

  • a. Clear the board.
  • b. Place two hydrogen atoms (H) and one oxygen atom (O) on the board.
  • c. Add bonds and or lone pairs of electrons until the electron count is zero.
  • d. Use the hint token to check your work
  • e. You have made the correct structure when you hear “you’ve made H2O, water.”
  • f. Fill in the blanks: Oxygen usually has _____ bonds and _____ lone pairs.

5. Follow the instructions below and build a Lewis structure of NH3 then fill in the blanks in the sentence below.

  • a. Clear the board.
  • b. Place three hydrogen atoms (H) and one nitrogen atom (N) on the board.
  • c. Add bonds and or lone pairs of electrons until the electron count is zero.
  • d. Use the hint token to check your work
  • e. You have made the correct structure when you hear “you’ve made NH3, ammonia.”
  • f. Fill in the blanks: Nitrogen usually has _____ bonds and _____ lone pairs.

6. Follow the instructions below and build a Lewis structure of CH4 then fill in the blanks in the sentence below.

  • a. Clear the board.
  • b. Place four hydrogen atoms (H) and one carbon atom (C) on the board.
  • c. Add bonds and or lone pairs of electrons until the electron count is zero.
  • d. Use the hint token to check your work
  • e. You have made the correct structure when you hear “you’ve made CH4, methane.”
  • f. Fill in the blanks: Carbon usually has _____ bonds and _____ lone pairs.

Lewis structures with multiple heavy atoms

Use the bonding patterns you learned in the previous section to help figure out the Lewis structure of compounds with multiple heavy atoms.

You may need to use double and triple bonds between atoms (except for hydrogen), to achieve an octet and use correct number of valence electrons from the atoms. A double bond counts as 4 electrons for the purpose of an octet around an atom, and a triple bond counts as 6 electrons. Do not forget to use your lone pairs, too.

You can either use the double bond or triple bond piece or you can make a double bond place the long sides of two single bonds next to each other. Likewise, make a triple bond by placing the long sides of three single bonds next to each other.

7. Formula:C2H6

  • a. Clear the board.
  • b. Place two carbon atoms (C) and six hydrogen atoms (H) on the board.
  • c. Use these atoms to build a Lewis structure of a molecule with the formula C2H6. You have made the correct structure when you hear “You’ve made C2H6, ethane.”

8. Formula: C2H4

  • a. Clear the board.
  • b. Place two carbon atoms (C) and four hydrogen atoms (H) on the board.
  • c. Use these atoms to build a Lewis structure of a molecule with the formula C2H4. You have made the correct structure when you hear “You’ve made C2H4, ethene.”

9. Formula: H2CO

  • a. Clear the board.
  • b. Place two hydrogen atoms (H), one carbon atom (C), and one oxygen atom (O) on the board.
  • c. Use these atoms to build a Lewis structure of a molecule with the formula H2CO. You have made the correct structure when you hear “You’ve made H2CO, formaldehyde.”  

10. Formula: CO2

  • a. Clear the board.
  • b. Place two hydrogen atoms (H), one carbon atom (C), and one oxygen atom (O) on the board.
  • c. Use these atoms to build a Lewis structure of a molecule with the formula H2CO. You have made the correct structure when you hear “You’ve made H2CO, formaldehyde.”

11. Formula: HCN

  • a. Clear the board.
  • b. Place one hydrogen atom (H), one carbon atom (C), and one nitrogen atom (N) on the board.
  • c. Use these atoms to build a Lewis structure of a molecule with the formula HCN. You have made the correct structure when you hear “You’ve made HCN, hydrogen cyanide.”

Congratulations! You are now a master Lewis structure builder!

Optional Lewis Structures Pre-lesson

Lewis structures are a way to show how atoms are connected to form molecules, including all of the electrons. There are 3 parts of a Lewis structure:

1. Atoms - In Lewis structures, atoms are represented by their chemical symbol (e.i. C for carbon), sometimes in a circle.

2. Bonds - Bonds are shown as lines that connect two atoms. Each bond counts for a total of 2 electrons. A single bond has one line, a double bond has 2 lines, and a triple bond has 3 lines.

3. Lone pairs of electrons - represented by two dots around an atom. It is made up of two electrons that are not used for bonding.

Now that you know what the components of a Lewis structure are, there are a few things you need to know about making Lewis structures.

Valence Numbers

Each atom has a specific number of valence electrons that it can use to bond. All of the electrons within a Lewis structure, including bonds and lone pairs, are valence electrons. Knowing the valence number of each atom will tell you how many electrons you can include in your Lewis structure. An atom’s valence number comes from its position on the periodic table. For example, carbon is in group 4 and has 4 valence electrons. When building a Lewis structure, the goal is to connect the atoms using bonds and add in lone pairs in a way that it uses all of the valence electrons.

Octet of Electrons

In a proper Lewis structure, each atom, with the exception of hydrogen, should have 8 electrons around it. This is known as an octet. When counting the number of electrons around an atom, each lone pair and each bond count as 2 electrons. For example, a chlorine atom with 1 bond and 3 lone pairs has 8 electrons because of the 2 electrons from the 1 bond and the 6 electrons from the 3 lone pairs (3 x 2), 2 + 6 = 8. Hydrogen, being in row 1 of the periodic table, can only have 2 electrons around it, thus it is called a duet.

Now that you know the components of a Lewis structure, and what valence electrons and octets are, you are ready to start building Lewis structures using the Lewis Structure Explorer!

Co- Author
Julia Winter

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