Atoms evaluator to grade chemistry answers

Updated 30 Aug 2024

The Atoms answer evaluator (expressionOchemEvalAtoms) compares the number of atoms of a given type, such as N or C, in a student’s response to the expected number of atoms. Both skeletal and mechanism questions support the Atoms evaluator.

Select Grade as Correct or Grade as Incorrect, then enter the conditions you want to be checked in student answers.
Select an “if” condition, whether:
total number of — Counts any atoms in the student’s answer.
largest number of contiguous — Counts the atoms of a given type which are contiguous and connected by bonds.
Enter a single element symbol, like N.
To grade the presence of H atoms drawn by the student —
Enter H here and select the explicit atoms only checkbox below.
Select an “is” comparison option.
“Is” comparison options and their mathematical equivalents
exactly
Student answer number = the number in this box
more than
Student answer number > the number in this box
fewer than
Student answer number < the number in this box
not exactly
Student answer number <> the number in this box
fewer than or equal to
Student answer number ≤ the number in this box
more than or equal to
Student answer number ≥ the number in this box
Enter the number of atoms.
Select explicit atoms only to grade only the explicitly drawn atoms.
Use this with the Show No H property to force students to draw the H atoms and then have this evaluator grade whether the right number of atoms are drawn.