Use the periodic table to predict shell structure and reactivity
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.
Run the investigation
- 1Choose lithium, sodium, and potassium and record their group and period numbers.
- 2Choose fluorine and chlorine and record their group and period numbers.
- 3Use the table categories to confirm that the first three are alkali metals and the last two are halogens.
- 4Record the valence-electron pattern and the shell count pattern implied by those positions.
Booting the lab…
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.
| Group number for Li / Na / K | |
|---|---|
| Group number for F / Cl | |
| Period number of Li | |
| Period number of Na | |
| Period number of K | |
| Valence-electron pattern you observe |
Answer the free response
You used the interactive table to compare alkali metals and halogens. (a) Explain why lithium, sodium, and potassium have similar chemical behavior even though their masses differ greatly. (b) Use your recorded periods to explain how the electron-shell structure changes from Li to Na to K and how that affects atomic radius. (c) Predict which element, sodium or chlorine, would more readily form a +1 ion and which would more readily form a −1 ion, and justify the prediction with valence electrons and Coulombic ideas rather than with memorized charges. (d) A student claims that moving down a group makes an element less reactive because the atom is larger. Evaluate that claim for Group 1 metals and explain what the table supports.
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