Track shell filling and infer valence behavior
Three steps, the way the exam actually works: work through the lab, write down your own observations, then answer a 6-point free response. What you recorded goes to the grader with your writing, so a conclusion that does not follow from your own evidence will cost you the point — exactly as it would with a real reader.
Predict before you look
- In the simple Bohr shell model, how many electrons fill the first shell and how many fill the second?
- Sodium has 11 electrons and chlorine has 17. Which of the two is closer to a full outer shell, and by how many electrons?
Nothing to submit here — these are to think through, so the prediction below is an informed one rather than a guess.
Commit to an answer now. It is not graded and being wrong costs nothing — the point is to have something specific to reconcile against once you have the data.
Answer every prediction to unlock the lab. A sentence is enough.
Run the investigation
Predictions first
The procedure and the simulation unlock once you have committed above. Observing before predicting is how a wrong intuition survives a lab intact.
Record what you found
This is your reading of the source, not ours. The grader sees them, so your conclusions have to follow from what you actually recorded.
| O shell distribution | |
|---|---|
| Na shell distribution | |
| Mg shell distribution | |
| Cl shell distribution | |
| Valence electrons in Na | |
| Valence electrons in Cl |
Answer the free response
The shell model is simple, but it is enough to explain much of periodic chemistry. (a) Using your recorded shell distributions, explain why sodium and magnesium are metals while oxygen and chlorine are nonmetals. (b) Predict the ion each would most commonly form and justify each prediction by the fewest-electron route to a stable outer shell. (c) Explain why sodium is more chemically similar to lithium than to magnesium even though sodium and magnesium are in the same period. (d) State one important limitation of the Bohr shell model for real atoms, while also explaining why it still works for AP-level periodic trends.
Sign in to have this graded and saved to your progress.