Isotopes are atoms that share the same number of protons but have a different number neutrons.

Question

Let's investigate what determines makes an atoms stable or not.

Which of the following are stable isotopes?

Hydrogen: 1-H ____________, 2-H ________, 3-H ____________
Helium: 3-He __________, 4-He__________, 5-He ____________
Lithium: 5-Li ___________, 6-Li__________, 7-Li ______________
Beryllium: 8-Be __________, 9-Be _________, 10-Be ___________
Boron: 10-B __________, 11-B __________, 12-B _______________
Carbon: 12-C___________, 13-C __________, 14-C ________________
Nitrogen: 13-N _____________, 14-N_____________, 15-N ________________
Oxygen: 16-O _____________, 17-O ___________, 18-O _____________
Fluorine: 18-F_____________, 19-F ___________, 20-F _______________
Neon: 20-Ne ________________, 21-Ne ____________, 22-Ne ____________

Stable or Unstable

Answer 1

Below is the determination of the stability of isotopes for the given elements:

Hydrogen:

• 1-H: Stable
• 2-H: Stable
• 3-H: Unstable (tritium is radioactive)

Helium:

• 3-He: Unstable (rare and radioactive)
• 4-He: Stable
• 5-He: Unstable (very short-lived)

Lithium:

• 5-Li: Unstable (radioactive)
• 6-Li: Stable
• 7-Li: Stable

Beryllium:

• 8-Be: Unstable (very short-lived)
• 9-Be: Stable
• 10-Be: Unstable (radioactive)

Boron:

• 10-B: Stable
• 11-B: Stable
• 12-B: Unstable (radioactive)

Carbon:

• 12-C: Stable
• 13-C: Stable
• 14-C: Unstable (radioactive)

Nitrogen:

• 13-N: Unstable (radioactive)
• 14-N: Stable
• 15-N: Stable

Oxygen:

• 16-O: Stable
• 17-O: Stable
• 18-O: Stable

Fluorine:

• 18-F: Unstable (radioactive)
• 19-F: Stable
• 20-F: Unstable (radioactive)

Neon:

• 20-Ne: Stable
• 21-Ne: Unstable (radioactive)
• 22-Ne: Unstable (radioactive)

In summary:

• Stable isotopes: 1-H, 2-H, 4-He, 6-Li, 7-Li, 9-Be, 10-B, 11-B, 12-C, 13-C, 14-N, 15-N, 16-O, 17-O, 18-O, 19-F, 20-Ne
• Unstable isotopes: 3-H, 3-He, 5-He, 5-Li, 8-Be, 10-Be, 12-B, 13-N, 18-F, 21-Ne, 22-Ne