Molecule drawing questions (Lewis structures)

Updated 29 Aug 2024

Complete molecule drawing questions on a computer, not on a smartphone or tablet.

Select "" Expand or collapse keyboard control (top toolbar) to show or hide keyboard instructions below the canvas.

To begin, select "" Launch Tips Tour to step through quick on-screen tips that identify options for drawing or editing molecules.

When available, open the Introduction to Mastering assignment and select the Introduction to Molecule Drawing Answers item. This assignment provides practice items for different kinds of questions. You can usually return to this assignment anytime during the course, even after its due date. If you completed this assignment, you can usually rework its items for practice.

  • From the top toolbar, select "" Undo, "" Erase (or "" Select and Erase), or even "" Reset, as needed.
  • If you select Erase — When you finish erasing, either select a new control or deselect Erase.
  • You can edit a submitted drawing answer as long as you have another chance to answer the question.

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See alternate instructions for chemical drawing using the Marvin chemical editor.

drawing of sodium formate molecule

  1. Place some common elements on the canvas.
    1. With "" Carbon selected in the toolbar, point to place it on the canvas. (Active buttons have a dark background.)
    2. Select "" Oxygen and place it on the canvas twice.
    3. Select "" Hydrogen and position it.
  2. Place an element from the periodic table on the canvas.
    1. Select "" Periodic Table to choose "" Sodium.
    2. Close the periodic table to place the sodium atom on the canvas.
  3. Add bonds between atoms.
    1. Select "" Double Bond from the toolbar, point on the top Oxygen atom on the canvas and drag to make the bond with the Carbon atom.
    2. Switch to "" Single Bond from the toolbar, point to Carbon on the canvas and add one bond to the Hydrogen atom and another bond to the lower Oxygen atom.
  4. Add electron pairs to an atom.
    1. Select "" Paired Electrons from the toolbar.
    2. Select the top Oxygen atom on the canvas (it changes color) twice to add 2 electron pairs.
    3. Select the bottom Oxygen atom on the canvas 3 times to add 3 electron pairs.
  5. Increase or decrease the charge for an atom.
    1. Select "" Increase Charge from the toolbar and select Sodium on the canvas.
    2. Select "" Decrease Charge from the toolbar and select the bottom Oxygen on the canvas.
  6. Select Submit to submit your answer.
    Important: If you move on to another item or close Mastering before selecting Submit, your molecular drawing work is not saved.


Work with molecule parts

  1. Select a common element from the toolbar, like "" Hydrogen.

    To see more elements —
    If needed, select "" Periodic Table to choose another element. Close the periodic table to return to the canvas.

  2. Place the atom on the canvas, whether in a blank area or on top of another atom to replace it.
  1. Select a bond type and an element from the toolbars.

    Tip: For a molecule with multiple bonds, it can be easier to select "" Unspecified Atom from the bottom toolbar. Replace the X atoms later with the specific atoms you want.

    To see more elements: If needed, select "" Periodic Table to choose an element. Close the periodic table to return to the canvas.

  2. Point and drag on the canvas to place the bond with the same element at both ends.
  3. To change one of the atom elements, deselect the active bond type from the toolbar. Then, select a different element from the toolbar and select the atom on the canvas to be replaced.
  1. Choose "" Select from the toolbar.
  2. Select the atom you want to erase on the canvas so that it turns green.
  3. Either press Delete from your keyboard or select  Erase.

    If the atom has a bond, the bond and any other connected atom will also be erased. This is true, even when only the atom is selected.

  4. If you pressed Delete in step 3, deselect Select. If you chose the Erase tool, deselect it.
  1. Choose "" Select from the toolbar.
  2. Select the atom on the canvas so that it turns green.
  3. Move the atom. If the atom has a bond, the bond angle will also be moved.
  1. Select a bond from the toolbar.
  2. Drag the bond on the canvas, whether to attach it to one or more atoms, replace a bond, or place in a blank area.

    If attaching to atoms — Be sure that each atom becomes selected (turns green). Otherwise, the currently active atom from the controls will appear at both ends.

    If replacing a bond — Position the new bond over the bond on the canvas. For single, double, and triple bonds, continue to select the bond on the canvas, until you see the bond type you want.

    Placing the "" Wedge Bond or "" Dash Bond over the same bond reverses the direction of the wedge or dash bond.

  1. Select a bond type and an element from the toolbars.

    For a molecule with multiple bonds — It can be easier to select "" Unspecified Atom from the bottom toolbar. Replace the X atoms later with the specific atoms you want.

    To see more elements — If needed, select "" Periodic Table to choose an element not shown on the toolbar. Close the periodic table to return to the canvas.

  2. Point and drag on the canvas to place the bond with the same element at both ends.
  3. Change one of the atom elements: (Optional)
    Deselect the active bond type from the toolbar. Then, select a different element from the toolbar and select the atom on the canvas to be replaced.
  1. Choose "" Select.
  2. On the canvas, select the atom at the end of the bond you want to change.
  3. Drag to lengthen or change the angle of a bond, as needed.
  1. Choose "" Select from the toolbar.
  2. Select the bond you want to erase on the canvas so that it turns green.
  3. Select "" Erase.

    If the bond is connected to one or more atoms without other bonds, these are also erased.

  4. When you’re finished, either select another control or deselect Erase.
  1. Select either "" Unpaired Electron or "" Paired Electrons.

    Adding two single dots on the canvas is NOT the same as adding an electron dot pair.

  2. Select an atom on the canvas to position the electron(s), which display as one or two dots.
  3. Select  Increase Charge or  Decrease Charge, as needed.
  1. Select "" Erase from the toolbar.
  2. On the canvas, select the electrons you want to erase.
  3. When you’re finished, either select another control or deselect Erase.
  1. Draw the molecule you want to identify as an ion.
  2. Select "" Square Brackets.
  3. On the canvas, select the molecule to enclose it in brackets.
  1. Select "" Erase from the toolbar.
  2. On the canvas, select the ion brackets you want to erase.
  3. When you’re finished, either select another control or deselect Erase.

The default charge of atoms is 0.

  1. Select "" Increase Charge.
  2. On the canvas, select the atom or bracket for which you want to increase the charge.
  3. Continue to select, until you see the charge value you want. The maximum charge is 8+.
  1. Select "" Decrease Charge.
  2. On the canvas, select the atom or bracket for which you want to decrease the charge.
  3. Continue to select, until you see the charge value you want. The minimum charge is 8-.


Basic Controls

Choose "" Select from the toolbar and then either select a molecule part (atom, bond, charge, or electron) on the canvas or select a group of items by dragging. Selected items change from black to green on the canvas.

  • To turn off Select mode so you can continue drawing: Choose Select again.
  • To deselect molecule parts: Either choose Select again or place your pointer in a blank area of the canvas while Select is still active.
  1. Select "" Erase.
  2. Select the molecule part or parts (atom, bond, charge, or electron) you want to delete.

    If you added molecule parts in a single action — All parts are erased, such as a bond with two atoms.

  3. To erase multiple parts (Optional) — Point and drag around the parts you want to erase. When you stop, the parts inside the square or rectangle you drew will be erased.
  4. When you’re finished, either select another control or deselect Erase.
  • Select "" Reset to return the canvas to its original state.
  • To undo your last action only, select Undo.
  • To erase parts of your drawing only, select Erase.
  • Select "" Undo to undo your last action.

    To delete only parts of your drawing — Select Erase.

    To start over completely — Select Reset.

  • Select "" Redo to redo your last action.

"" Zoom In: Select to enlarge your view of the drawing.

"" Zoom Out: Select to reduce your view of the drawing.

"" Zoom Fit: Use to enlarge your drawing to fit the canvas with some white space around it. If the drawing becomes too large: Select Undo. (Using Zoom Out only reduces the image in very small increments.)

Select "" Copy Answer Strings to copy the correct expression, answer string, and parameters to your clipboard.

When you copy the correct answer, you can compare the answer string to your own drawing if you believe your answer was incorrectly marked wrong.

To open the periodic table —
Select "" Periodic Table. Close the periodic table to return to the drawing canvas.

To change your view of the periodic table —
Choose one of the following color schemas to refer to when drawing molecules. Your selection remains active if you close the periodic table and then return to it within the same Mastering session.

  • CPK: Active automatically. Choosing CPK makes the element names appear in CPK colors. These colors are commonly used to distinguish atoms of different chemical elements in molecular ball and stick models.
  • Standard state: Select to see the standard state of elements in the periodic table, whether gas, solid, liquid, or other.
  • Blocks: Select to distinguish which block an element belongs to. Use the color legend to identify s Block (includes Group 1 alkali metals with one valence electron & Group 2 alkali earth metals with two valence electrons), d Block (transition metals with electrons in d orbitals), p Block (elements with valence electrons in the p orbital), and f Block (inner transition metals with electrons in f orbitals).
  • Metals/Nonmetals: Select for elements to appear classified as metallic or nonmetallic. Use the color legend to identify elements labeled as alkali metal, alkaline earth metal, other metal, metalloid, transition metal, or nonmetal.


Grading of molecule drawing answers

Similar to other answers, Mastering automatically grades molecule drawing answers. If you think you’re been graded inaccurately, please contact your instructor.