Question 19M.2.sl.TZ2.a
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.sl.TZ2.a |
| Level | sl | Paper | 2 | Time zone | TZ2 |
| Command term | Suggest | Question number | a | Adapted from | N/A |
Rhenium, Re, was the last element with a stable isotope to be isolated.
Before its isolation, scientists predicted the existence of rhenium and some of its properties.
Suggest the basis of these predictions.
[2]
gap in the periodic table
OR
element with atomic number «75» unknown
OR
break/irregularity in periodic trends [✔]
«periodic table shows» regular/periodic trends «in properties» [✔]
This nature of science question generated a lot of discussion among teachers. Some in support of such questions and others concerned that it takes a lot of time for candidates to know how to answer. Some teachers thought it was unclear what the question was asking. It is pleasing that about a quarter of the candidates answered both parts successfully and many candidates gained one mark usually for “periodic trends”. However, some candidates only focused on one part of the question. Quite a few candidates discussed isotopes, probably thrown off by the stem. A teacher was concerned that since transition metals are not part of the SL syllabus that Re was a bad choice, however, the question did not really require any transition metal chemistry to be answered.
