Question 1
Paper 2Medium10 marksA representative sample of natural boron is characterized for use in a neutron-absorbing material. It contains the isotopes ¹⁰₅B and ¹¹₅B. The relative isotopic masses and relative atomic mass of the sample are:
| Isotope | Relative isotopic mass |
|---|---|
| ¹⁰₅B | 10.0129 |
| ¹¹₅B | 11.0093 |
The relative atomic mass, Aᵣ, of the sample is 10.811.
(a)[3]
For the ion ¹⁰₅B⁺, state the number of protons, neutrons and electrons.
(b)[2]
Explain why ¹⁰₅B and ¹¹₅B are isotopes.
(c)[3]
Assuming the sample contains only these two isotopes, determine the percentage abundance of ¹⁰₅B. Give your answer to three significant figures.
(d)[2]
A student claims that ¹⁰₅B and ¹¹₅B must have identical physical properties because they have the same number of protons. Explain why this claim is not justified.