Question

The graph shows all of the stable isotopes of elements according to the numbers of protons and neutrons in their nuclei.

A graph titled zone of nuclear stability with number of protons from 0 to 80 on the x-axis with number of neutrons on the y-axis from 0 to 140. There are two lines, one with a slope of 1 from (0, 0). The other line has points of (20, 24), (40, 52) and (60, 120) labeled stability zone.

Which statements are supported by the graph? Check all that apply.

For large atoms, more neutrons than protons are needed to be stable.
Nuclei that have 90 or greater protons are always radioactive.
Atoms must have equal numbers of protons and neutrons to be stable.
Atoms that have less than 10 protons do not need neutrons to be stable.

Answer 1

Only the first statement is supported.

- For large atoms, more neutrons than protons are needed to be stable. — supported: the stability band lies above the N=Z line for high proton numbers (N>Z).
- Nuclei that have 90 or greater protons are always radioactive. — not supported: the graph only shows up to Z≈80, so it does not provide information about Z≥90.
- Atoms must have equal numbers of protons and neutrons to be stable. — not supported: the graph shows many stable isotopes with N≠Z, especially for heavier elements.
- Atoms that have less than 10 protons do not need neutrons to be stable. — not supported: the graph shows small nuclei generally have N≈Z (not N=0); only hydrogen-1 (Z=1, N=0) is a neutron‑less stable case.