| 1. | C |
| 2. | B |
| 3. | D |
| 4. | B |
| 5. | C |
| 6. | C |
| 7. | B |
| 8. | B |
| 9. | C |
| 10. | C |
| 11. | C |
| 12. | |
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| 13. | |
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| 14. | |
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| 15. | |
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| 16. | |
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| 17. | |
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| 18. | |
| A sodium ion is formed by loss of a single, outer electron, leading to a reduction in the number of occupied energy levels / shells. 2,8,1 becomes 2,8.
A chlorine atom is formed by the addition of a further electron, filling the outer energy level/ shell. 2,8,7 becomes 2,8,8. The chlorine ion has 3 occupied energy levels/ shells, the sodium has only two. |
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| 19. | |
| As the size of the ion increases, the enthalpy of lattice formation decreases | |
| 20. | |
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