Nuclear Stability ✏ Chemistry In a Nutshell

Rucete ✏ Chemistry In a Nutshell

1. Key Factors Affecting Nuclear Stability

• The neutron-to-proton (N/Z) ratio determines nuclear stability.
• Stable nuclei of light elements (low atomic number) have an N/Z ratio close to 1.
• For heavier elements, the stable N/Z ratio increases above 1 due to repulsive proton-proton forces.

 

 

2. Magic Numbers (Stable Nuclei)

• Certain nuclei with specific numbers of protons or neutrons are more stable:
  • 2, 8, 20, 50, 82, 126 are considered "magic numbers".
  • These nuclei tend to be more stable than others with different numbers.
    

 

 

3. Effect of Even vs. Odd Protons/Neutrons

• Nuclei with even numbers of both protons and neutrons are more stable.
• Nuclei with odd numbers are generally less stable.

 

 

4. Radioactive Isotopes and Decay

• Unstable isotopes undergo radioactive decay to achieve stability.
• Types of decay depend on mass number and atomic number:
  • If mass number > stable atomic weight → Beta (β⁻) decay occurs.
  • If mass number < stable atomic weight → Positron (β⁺) emission or electron capture occurs.
  • If atomic number > 60 → Alpha (α) decay occurs.
  • If atomic number > 90 → Spontaneous fission occurs.

 

 

5. Polonium and Other Unstable Elements

• Polonium (Atomic number 84) and its isotopes are always radioactive.

 

 

In a nutshell

Condition	Type of Decay
Mass number > stable isotope	Beta (β⁻) decay
Mass number < stable isotope	Positron (β⁺) emission or electron capture
Atomic number > 60	Alpha (α) decay
Atomic number > 90	Spontaneous fission

 

Stable nuclei have N/Z close to 1 for light elements, and higher for heavy elements.

Even protons & neutrons = more stability.

Decay occurs when the nucleus is too heavy or has the wrong N/Z ratio.