Final answer:
Rubidium's two most reasonable isotopes are rubidium-85 and rubidium-87, with Rb-85 being more common due to its closer atomic mass to 85.47. The radioactive isotope carbon-14 has six protons and eight neutrons.
Step-by-step explanation:
The atomic mass of rubidium is 85.47. The two most reasonable isotopes of rubidium are rubidium-85 and rubidium-87.
Rubidium-85 has an atomic mass of 84.91178974 amu and contains 37 protons, as it is a neutral atom. To determine the number of neutrons, we subtract the number of protons from the atomic mass:
Number of neutrons = Atomic mass - Number of protons
Number of neutrons = 84.91178974 amu - 37 protons
Number of neutrons ≈ 48
Rubidium-87 has an atomic mass of 86.90918053 amu and contains 37 protons, as it is a neutral atom. To determine the number of neutrons, we subtract the number of protons from the atomic mass:
Number of neutrons = Atomic mass - Number of protons
Number of neutrons = 86.90918053 amu - 37 protons
Number of neutrons ≈ 50
Now, regarding the abundance of these isotopes in nature, rubidium-85 should be more common because it has a lower atomic mass compared to rubidium-87. This suggests that rubidium-85 is more stable and thus more abundant.
Moving on to the second question, carbon-14 has an atomic number of 6, which means it has 6 protons. To determine the number of neutrons, we subtract the number of protons from the atomic mass:
Number of neutrons = Atomic mass - Number of protons
Number of neutrons = 14 amu - 6 protons
Number of neutrons = 8
Therefore, carbon-14 has 6 protons and 8 neutrons.