Summary

In this activity, students will use free online computational modeling software, with guided inquiry parameters, to learn how atomic properties of atoms in a molecule affect the shape and stability of the molecule.

Grade Level

High School

NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

• HS-PS1-4: Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.
• HS-PS2-4: Use mathematical representations of Coulomb’s Law to describe and predict the electrostatic forces between objects.
• HS-PS3-5: Develop and use a model of two objects interacting through electric or magnetic fields to illustrate the forces between objects and the changes in energy of the objects due to the interaction.
• Scientific and Engineering Practices:
  • Using Mathematics and Computational Thinking
  • Developing and Using Models

Objectives

By the end of this activity, students should be able to:

• Explain how atomic properties affect the energy and stability of arrangements of atoms in a molecule.
• Describe how bonded atoms will spread out around a central atom in three-dimensional space.

Chemistry Topics

This activity supports students’ understanding of:

• Covalent bonding
• Lewis structures
• VSEPR theory

Time

Teacher Preparation: 30-45 minutes

Lesson: 45 minutes

Materials (per group of 2-3 students)

• 1 laptop or device
• 2 bar magnets
• 1 plastic bin (large enough for 2 bar magnets to be separated)
• Access to WebMO

Safety

• No specific safety precautions need to be observed for this activity.

Teacher Notes

• Teachers can learn more about this topic by accessing the author’s corresponding article, Computational Chemistry in the High School Classroom, published in the May 2026 issue of Chemistry Solutions.
• Prior to using this activity in the classroom, teachers are encourage to explore WebMO themselves and complete Part 3 of the activity in order to fully understand the instructions and functions of the program.

Student Pre-Requisite Knowledge:

• Draw Lewis dot diagrams for atoms based on valence electrons.
• Draw Lewis structural diagrams for simple molecules.
• Compare relative atomic properties, radius and electronegativity, based on group and period trends.

Activity Background:

• The intent of this activity is to introduce students to the function of computational chemistry, so they can begin to think beyond the physical models that they work with in class and to consider why the models look the way they do.
• It is designed to be an activity that builds up to but does not specifically include VSEPR theory and molecular geometry, as it provides a foundation for making predictions about the arrangements of atoms in simple molecules.
• Rather than analyzing bond angles, the directions have students measure the distance between atoms. This can be easily modified to measure bond angles if the teacher prefers. Directions for measuring bond angles are included in the Directions Page for WebMO.
• The goal is that this activity also appeals to students who have interests in computer programming or coding, as it is a great example for potential career paths for people who may enjoy chemistry but prefer computers as opposed to working in a lab.

Activity Outline:

• Begin the activity with Part 1. Students can read (silently or aloud) the intro to Computational Chemistry section. Explain that the activity they will work through allows them a glimpse into some simple types of problems that computational chemists work on.
• Students complete the section, “All chemical substances are made of charged particles” by reading and answering questions 1a-b.
• Review answers and highlight main points:
  • The electrons move around the atom.
  • All electrons will repel each other, more so when they are closer to each other.
  • All electrons will be attracted to the nucleus, which acts like a single highly positive charge since the protons are all condensed together.
• Students read (silently or aloud) the 2 paragraphs, “Finding a balance” and “Magnets as a familiar analogy” to start Part 2.
• Quick “Explore” activity with magnets:
  • Distribute 2 bar magnets and a plastic bin to each group.
  • Allow about 3 minutes for them to play with the magnets.
• Students complete questions 2-3 (be sure they read the intro to the questions).
• Review the main points:
  • Magnetic fields and electric fields act in similar ways.
  • The “north” and “south” parts of a bar magnet are an analogy for the separated positive and negative particles in an atom (protons and electrons).
  • North attracts south, like positive attracts negative.
  • N-N or S-S repel each other, like positive-positive or negative-negative.
• Students read the next paragraphs, then teachers should review major points together:
  • Atoms in a molecule are bonded together
  • Their arrangement within that molecule is based on a balance of attractive and repulsive forces
  • Heat of formation can be used to compare the stability of different arrangements (a more negative heat of formation value represents a molecule that is more stable and resistant to change)
• Part 3: Take on the Role of a Computational Chemist
  • At this point, you should hand out the “Directions Page for WebMO”. The student handout instructs students what steps to carry out and the directions page gives details and hints about each feature they will use.
  • Below is a screenshot of the job manager students will see (with names and initials blacked out). The “Name” of the job is automatically filled in with the molecule they create. Direct students to replace the molecule name with their names, initials, or some other label you assign to them, so they know which job is theirs. If 24 students work on this at the same time, there will be 24 jobs that are simply labeled “CH4”. Also note that this is a live and public server, so give them whatever directions they need to ensure they don’t use offensive language or anything that is personally identifiable when changing the job name.

• Students should work through the remainder of the worksheet on their own or in small groups.
• It is built as an inquiry-based lesson, so the teacher should check in with each group frequently to re-direct or to give feedback as needed.
• An Answer Key document is provided for teacher reference.