Which isotope of krypton has 50 neutrons?

• A. Kr-78
• B. Kr-80
• C. Kr-86
• D. Kr-82

Answer: (C)

Verified step by step guidance

1. Recall that the number of neutrons in an isotope is given by the difference between the mass number (A) and the atomic number (Z): \(\text{Number of neutrons} = A - Z\).
2. Identify the atomic number (Z) of krypton (Kr), which is 36. This means every krypton atom has 36 protons.
3. For each isotope option, subtract 36 from the mass number to find the number of neutrons. For example, for Kr-78, neutrons = \$78 - 36$.
4. Calculate the neutron number for each isotope: Kr-78, Kr-80, Kr-82, and Kr-86, and compare each result to 50 neutrons.
5. The isotope whose mass number minus 36 equals 50 neutrons is the correct answer.