What does the number 84 in the name krypton-84 represent?

• A. The atomic number of krypton
• B. The mass number of the krypton isotope
• C. The number of electrons in krypton
• D. The number of neutrons in krypton

Answer: (B)

Verified step by step guidance

1. Understand that the number in the name of an isotope, such as krypton-84, refers to a specific property of that isotope.
2. Recall that the atomic number represents the number of protons in an element, which is constant for all isotopes of that element.
3. Recognize that the mass number is the total number of protons and neutrons in the nucleus of the isotope.
4. Know that the number of electrons in a neutral atom equals the atomic number, not the number given in the isotope name.
5. Therefore, the number 84 in krypton-84 represents the mass number, which is the sum of protons and neutrons in that isotope.