Chemistry - f-block Question with Solution | TestHub
Use the 14-element series convention: lanthanoids Ce-Lu and actinoids Th-Lr. Let count elements in these series with no stable isotopes. Let count lanthanoids with metallic atomic radius greater than Eu in the stated data.
Atomic radii (pm):
Ce: 183
Pr: 182
Nd: 181
Pm: 181
Sm: 180
Eu: 199
Gd: 180
Tb: 178
Dy: 177
Ho: 176
Er: 175
Tm: 174
Yb: 173 (NCERT 2021-22, Table 8.9)
Lu: 175 (WebElements empirical atomic radius)
Use only these values for . Let be the highest oxidation state of Am listed in the NCERT textbook convention. Let count the textbook natural actinoids Th, Pa, and U only, excluding trace decay-chain occurrences. Find .
Answer:
Solution:
Promethium has no stable isotopes; all 14 actinoids Th-Lr are radioactive. Thus a = 15. All stated atomic radii are below Eu's 199 pm, so b = 0. NCERT lists Am oxidation states up to +6; under that convention c = 6. The specified category includes only Th, Pa and U, so d = 3. The answer is 15 + 0 - 6 - 3 = 6. Radius data for Ce-Yb and Am oxidation states: NCERT Chemistry Part I (2021-22), Chapter 8, Tables 8.9 and 8.11. The stated Lu radius is WebElements' empirical value, 175 pm.
