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Checking Radius Claims in a Model Ion Sorter 4 questions
Checking Radius Claims in a Model Ion Sorter
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A classroom ion sorter groups particles by the modeled distance of their outer electrons from the nucleus. The class compares a neutral magnesium atom and two positive ions. The table reports proton counts and the number of electrons in each occupied shell.
| Particle | Protons | Electrons in occupied shells |
|---|---|---|
| Mg atom | 12 | 2, 8, 2 |
| Mg2+ ion | 12 | 2, 8 |
| Na+ ion | 11 | 2, 8 |
Question 1
Explain why the magnesium ion is smaller than the neutral magnesium atom in the model. Use the shell information.
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Question 2
Which pair can the class compare to study a difference in proton count while keeping the electron arrangements the same?
- Mg atom and Mg²⁺ ion
- Mg atom and Na⁺ ion
- Mg²⁺ ion and Na⁺ ion
- All three particles together
For particles with identical electron arrangements, the model predicts that a nucleus with more protons pulls the outer electrons closer. The class now adds an Al3+ model. It has 13 protons and the same electron arrangement, 2, 8.
Question 3
Rank Na⁺, Mg²⁺, and Al³⁺ from greatest to least modeled radius. Explain using the model rule.
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Question 4
A student wants to apply the same rule to rank the neutral Mg atom and Al³⁺ using their proton counts alone. Explain why that comparison does not meet the stated condition of the rule.
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