WAEC 2010 Physics · Question 19
A nuclide represented as has a neutron-proton ratio of
Options
- A.0.5
- B.0.8
- C.1.2
- D.1.5
Answer: C. 1.2
Explanation written with AI and checked against the answer key
Analyze the question: We need the ratio of neutrons to protons in the nuclide ⁷⁰₃₂X.
Concept: For a nuclide written as ᴬ_ZX:
- A = mass number (protons + neutrons) = 70
- Z = atomic number (number of protons) = 32
- Number of neutrons N = A − Z
Solution:
- Protons = Z = 32
- Neutrons = A − Z = 70 − 32 = 38
- Neutron-proton ratio = N / Z = 38 / 32 = 1.1875 ≈ 1.2
Checking the options:
- A (0.5): too low, since neutrons are more than protons here
- B (0.8): this is below 1, so it's wrong
- C (1.2): matches 1.1875 rounded to one decimal place ✔
- D (1.5): would need about 48 neutrons, which is not the case
Tip: Always remember "Neutrons = A − Z" (the top number minus the bottom number). Then divide by the number of protons (the bottom number) for the n/p ratio. If the options are rounded, pick the closest one: 38/32 ≈ 1.19, which rounds to 1.2.
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