DP Chemistry (first assessment 2025)
Question 21M.2.SL.TZ2.a(ii)
| Date | May 2021 | Marks available | [Maximum mark: 2] | Reference code | 21M.2.SL.TZ2.a(ii) |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Explain | Question number | a(ii) | Adapted from | N/A |
a(ii).
[Maximum mark: 2]
21M.2.SL.TZ2.a(ii)
Explain the decrease in radius from Na to Na+.
[2]
Markscheme
Na+ has one less energy level/shell
OR
Na+ has 2 energy levels/shells AND Na has 3 ✓
less shielding «in Na+ so valence electrons attracted more strongly to nucleus»
OR
effective nuclear charge/Zeff greater «in Na+ so valence electrons attracted more strongly to nucleus» ✓
Accept “more protons than electrons «in Na+»” OR “less electron-electron repulsion «in Na+»” for M2.
Syllabus sections
Structure 2. Models of bonding and structure » Structure 2.1—The ionic model » Structure 2.1.1—When metal atoms lose electrons, they form positive ions called cations. When non-metal atoms gain electrons, they form negative ions called anions. Predict the charge of an ion from the electron configuration of the atom.