Grading parameters for Lewis structure answers

Updated 08 Feb 2023

The grading and display parameters for a chemical drawing - Lewis correct answer control how student work is graded and the appearance of some elements as a student draws, like whether bonds are shown as lines or dots. You should set the same grading parameters for any student incorrect answers you supply for wrong answer feedback.

  • You can set most grading options from the toolbar on the left or you can copy Parameters from another Lewis answer.
  • Applied grading and display settings appear as a string in the Parameters field for a chemical drawing - Lewis answer.

  1. Select Edit Answer next to Correct Answer or for an incorrect student response (If the student answers) in wrong answer feedback.
  2. Look in the Parameters field, below the drawing canvas.

    For the meaning of the codes in this field, see the next section.

Point to grading options in the Lewis drawing tool (left toolbar) to see their meanings as they apply to the current question. Any applied setting appears with a shaded background. For example:

For this question, you should include all nonbonding electrons (lone pairs and radicals) if there are any.

The codes in a Parameters string are separated with the character “&”.

Lewis Grading Parameter
 Description
H Grade hydrogens

 

Default = On

In the Parameters string: hydrogens=1

The hydrogen grading option applies only to carbon atoms, since hydrogen atoms are automatically graded for all non-carbon atoms.


  • When this option is on (=1), students must draw ALL hydrogen atoms, including those bonded to carbon atoms.
  • When this option is off (=0), students don’t need to draw hydrogen bonds.
E/Z Grade cis/tran isomers

Default = Off

In the Parameters string: isometry=0

You’ll likely want to turn this grading on for alkenes.


  • When this option is off (=0), Isometry across C=C bonds (cis vs. trans) are ignored during grading.
  • When this option is on (=1), students must enter the correct isomer bonds (cis vs. trans).
R/S Grade chirality

 

Default = Off

In the Parameters string: chirality=0
  • When this option is off (=0), chirality is ignored in grading.
  • When this option is on (=1), chirality is included in grading. Hydrogen atoms must also be graded if there is a hydrogen atom on a chiral carbon.

Choose wedge and dash bonds from the bonds area of the toolbar.

  • For the correct answer: Solid wedge bonds must have the narrow end on the chiral carbon. Dash bonds can have either the narrow end or the wide end on the chiral atom, as long as the direction is consistent.
  • For a wrong answer: You can create wedge bonds and hash bonds in either direction.

Note: Chiral grading is not compatible with Fischer projections or Haworth structures.
2 dots, arranged vertically
Grade lone pair electrons

 

Default = On

In the Parameters string: nonbonding=1
  • When this option is on (=1), students must include all nonbonding electrons (including lone pairs and radicals) if there are any.
  • When this option is off (=0), lone pairs and radicals are ignored in grading.
I Set initial state

 

Default = Off

In the Parameters string: initial=0

 

Select this option to provide an initial Lewis structure for questions in which students must select a portion of the drawing. How to provide a Lewis structure (You must draw before applying Set initial state.)


  • When this option is off (=0), a Lewis structure is NOT initially provided on the canvas when students view the question.
  • When this option is on (=1),a Lewis structure IS initially provided on the canvas when students view the question.
H, 2 dots arranged vertically, and H Show bonds as lines or dots

 

Default = Off

In the Parameters string: bonds=0
  • When this option is off (=0), all bonds appear as lines on the canvas.
  • When this option is on (=1), all bonds appear as dots on the canvas.
Draw, Both, Select

 

Default = Draw

In the Parameters string: qtype=draw

Student work is graded based on the question type, whether they need to draw, select, or both draw and select.

The type is applied when you either select one of these types from the top toolbar or as part of a copied Parameters string.