例句與造句

1. The second-most stable radioisotope is the synthetic lead-202, which has a half-life of about 53, 000 years, longer than any of the natural trace radioisotopes.
2. Thorium-232 ( 232 Th ), which has 142 neutrons, is the most stable isotope of thorium and accounts for nearly all natural thorium, with six other natural isotopes occurring only as trace radioisotopes.
3. All of the alkaline earth metals except magnesium and strontium have at least one naturally occurring radioisotope : beryllium-7, beryllium-10, and calcium-41 are trace radioisotopes, calcium-48 and barium-130 have very long radioactive.
4. All of the alkali metals except lithium and caesium have at least one naturally occurring radioisotope : sodium-22 and sodium-24 are trace radioisotopes produced cosmogenically, potassium-40 and rubidium-87 have very long half-lives and thus occur naturally, although it has no naturally occurring radioisotopes . ( Francium had not been discovered yet at that time . ) The natural long-lived radioisotope of potassium, potassium-40, makes up about 0.012 % of natural potassium, and thus natural potassium is weakly radioactive.
5. The most stable of them ( after 232 Th ) are 230 Th with a half-life of 75, 380 years, 229 Th with a half-life of 7, 340 years, 228 Th with a half-life of 1.92 years, 234 Th with a half-life of 24.10 days, and 227 Th with a half-life of 18.68 days : all of these isotopes occur in nature as trace radioisotopes due to their presence in the decay chains of 232 Th, 235 U, 238 U, and 237 Np ( produced in minute traces in nuclear reactions in uranium ores ).
6. It's difficult to find trace radioisotope in a sentence. 用trace radioisotope造句挺難的