Final answer:
The hyphenated name of the unknown isotope is Cl-35, as it is consistent with the rules of nuclear conservation and corresponds to an isotope of chlorine with a mass number of 35. Option B is correct.
Step-by-step explanation:
The question asks for the hyphenated name of an unknown isotope, given that one isotope's hyphenated name is Br-81. To identify the correct answer from the options provided, we need to consider the mass number and atomic number of each element. The isotope with a hyphenated name typically consists of the element's symbol followed by the mass number, which is the sum of its protons and neutrons. The hyphenated name of the unknown isotope can be determined by understanding the format of isotope notation. Isotope notation includes the element symbol followed by a hyphen and the mass number.
From the provided options, Cl-35 is the correct hyphenated name for the unknown isotope. This is confirmed by information stating that chlorine (Cl) has an atomic number of 17 and, through nuclear conservation, a particular isotope of chlorine must have a mass number of 35 (Z = 16 - (-1) = 17, A = 35 - 0 = 35). This leads us to the correct hyphenated name for chlorine with a mass number of 35, which is Cl-35.