| Date | November 2016 | Marks available | 2 | Reference code | 16N.3.hl.TZ0.28 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 28 | Adapted from | N/A |
Question
Technetium-99m is the most widely used medical radioisotope. It is usually made on-site in medical facilities from isotopes of molybdenum.
Deduce equations for the following nuclear reactions:
(i) Molybdenum-98 absorbs a neutron.
(ii) The isotope produced in (a) (i) decays into technetium-99m.
Molybdenum-99 has a half-life of 66 hours, while technetium-99m has a half-life of 6 hours. Outline why technetium-99m is made on-site.
Outline two reasons, other than its half-life, why technetium-99m is so useful in medical diagnosis.
Outline the nature of the radioactive waste that is generated by the use of technetium-99m in medical diagnosis.
Markscheme
i
9842Mo + 10n → 9942Mo
Accept 98Mo + 1n/n → 99Mo.
ii
9942Mo→99m43Tc+0−1β
Accept “ 0−1e” for “ 0−1β”.
Accept “ 99Mo→99mTc+β”.
Accept “ 0−1e/e−/e” for “β”.
Do not penalize “ 99Tc” for “ 99mTc”.
molybdenum-99 can be easily transported «before it decays»/more stable
OR
«most of» technetium-99m will decay during transportation
Do not accept just “short half-life of Tc-99m”
emits gamma rays
OR
emissions escape from body
OR
emissions detected by gamma camera
OR
radiation dose is low
chemically reactive/versatile/transition metal bonds to a range of «biologically active» substances
Do not accept “short half-life of Tc-99m”.
Accept “energy of photons produced is «relatively» low” and “no high energy beta emission” for M1.
Accept “…has ability to form tracers” for “…bonds to a range of «biologically active» substances".
low-level «radioactive» waste/LLW
OR
small amounts of ionizing radiation for short time
