The rule that the mass number of stable isotopes is always at least twice the atomic number is true for all nuclides except hydrogen-1 and

Question

Quizplus · Accepted Answer

The rule states that for stable isotopes the mass number is at least twice the atomic number. Hydrogen-1 has a mass number of 1 and an atomic number of 1, so it violates the rule. Among the given options, only helium-3 has a mass number that is not at least twice its atomic number (mass number is 3, atomic number is 2). Therefore, the answer is B.

The Rule That the Mass Number of Stable Isotopes Is