• 6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.
• 9-12: 4D/H2. The number of protons in the nucleus determines what an atom's electron configuration can be and so defines the element. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Atoms form bonds to other atoms by transferring or sharing electrons.

• 9-12: 4E/H4. Chemical energy is associated with the configuration of atoms in molecules that make up a substance. Some changes of configuration require a net input of energy whereas others cause a net release.

• 9-12: 4G/H2b. At the atomic level, electric forces between electrons and protons in atoms hold molecules together and thus are involved in all chemical reactions.

• 6-8: 11B/M1. Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly. They are also used for processes that are too vast, too complex, or too dangerous to study.
• 6-8: 11B/M4. Simulations are often useful in modeling events and processes.
• 9-12: 11B/H5. The behavior of a physical model cannot ever be expected to represent the full-scale phenomenon with complete accuracy, not even in the limited set of characteristics being studied. The inappropriateness of a model may be related to differences between the model and what is being modeled.

Designed for physical science courses, this interactive module explores factors that cause atoms to form or break bonds with each other. It's sequenced so that middle school students can tackle the concepts, but can also be adapted as a short exercise for high school.

• Physical Sciences K-8 Molecular Structures and Bonding Unit
• Physics First Molecular Structures and Bonding Unit
• Conceptual Physics Molecular Structures and Bonding Unit
• Algebra-Based Physics Molecular Structures and Bonding Unit