We're asked to** determine which of the following isotopes** are **expected to be stable**.

Recall that **Isotopes** represent atoms of an element that contain the same atomic number (same number of protons), but different mass numbers (different number of neutrons) and can be written as:

In terms of **stability of isotopes**, we use the **neutrons to protons (n/p) ratio**:

- Isotopes with
**neutrons to protons (n/p) ratio**are considered__close to 1__**stable**- For atoms with
**lower atomic numbers****n = p****→****(n/p) ≈ 1**

- For atoms with
- Isotopes with
**neutrons to protons (n/p) ratio**are considered__greater than 1__**unstable***will**undergo radioactive decay*- For atoms with
**higher atomic numbers** **n > p****→****(n/p) > 1**

**For this problem, we need to do the following steps:**

*Step 1**: Determine the # of protons, p based on the atomic number of each isotope using the Periodic Table *

*Recall that the atomic # = # of protons (p)*

*Step 2**: Determine the # of neutrons, n for each isotope*

*Recall that the mass # = # of neutrons (n) + # of protons (p) *

*Step 3**: Calculate the n/p ratio to determine its stability *

Which of the following isotopes would you expect to be stable?

a. ^{208}Pb

b. Carbon-12

c. Uranium 235

d. ^{4}He

e. ^{208}Po

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Band of Stability concept. You can view video lessons to learn Band of Stability. Or if you need more Band of Stability practice, you can also practice Band of Stability practice problems.

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