Which statement about the Chart of Nuclides is true?

Which statement about the Chart of Nuclides is true?

• A. Gray square indicates stable isotopes or isotopes with half-life greater than 5e8 years
• B. A black triangle in the lower right hand corner indicates a fission product of U-235
• C. Protons are plotted along the vertical axis
• D. Neutrons are plotted along the horizontal axis

Answer: (A)

On the Chart of Nuclides, shading communicates stability: gray squares indicate nuclides that are stable or have half-lives so long they effectively don’t decay on geological timescales. A practical convention is to mark as stable those with half-lives beyond about 5×10^8 years, which helps physicists and health professionals quickly identify isotopes that won’t pose decay hazards in most contexts. The axes are arranged with proton number (Z) on the horizontal axis and neutron number (N) on the vertical axis, so protons are not on the vertical axis and neutrons are not on the horizontal axis. This standardized layout means the statements about protons being vertical and neutrons being horizontal are not correct. Regarding fission products, there isn’t a universal rule that a black triangle in the lower right corner denotes a fission product of U-235; charts use different symbols for various features, and this specific marker isn’t a standard definition.

On the Chart of Nuclides, shading communicates stability: gray squares indicate nuclides that are stable or have half-lives so long they effectively don’t decay on geological timescales. A practical convention is to mark as stable those with half-lives beyond about 5×10^8 years, which helps physicists and health professionals quickly identify isotopes that won’t pose decay hazards in most contexts.

The axes are arranged with proton number (Z) on the horizontal axis and neutron number (N) on the vertical axis, so protons are not on the vertical axis and neutrons are not on the horizontal axis. This standardized layout means the statements about protons being vertical and neutrons being horizontal are not correct.

Regarding fission products, there isn’t a universal rule that a black triangle in the lower right corner denotes a fission product of U-235; charts use different symbols for various features, and this specific marker isn’t a standard definition.