Neutron-to-proton ratio calculation: an element has mass number A = 80 and atomic number Z = 40. What is the neutron-to-proton ratio N/Z?

Introduction / Context:
Quickly determining neutron and proton counts from A and Z is a core skill in nuclear chemistry and reactor physics. Ratios like N/Z indicate stability trends and help check bookkeeping in reaction equations.

Given Data / Assumptions:

• Mass number A = 80.
• Atomic number Z = 40.
• Definitions: Z = protons, N = neutrons = A − Z.

Concept / Approach:
Compute neutrons directly from A − Z, then form the ratio N/Z. Many medium-mass stable nuclides have N/Z near 1 to slightly above 1; this example lands exactly at 1.

Step-by-Step Solution:
Compute N: N = A − Z = 80 − 40 = 40.Compute N/Z: 40 / 40 = 1.Select the option equal to 1.

Verification / Alternative check:
Proton count equals neutron count here, consistent with many nuclides around the middle of the chart where N ≈ Z.

Why Other Options Are Wrong:
0.5 implies N = 20 with Z = 40 (not the case).2 implies N = 80 with Z = 40 (exceeds A).4 is impossible since N cannot exceed A.

Common Pitfalls:
Swapping A and Z; forgetting to subtract Z from A to get N; simplifying the ratio incorrectly.

Final Answer:
1